diff --git a/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunner.java b/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunner.java
index 118855ccc46..7a866d5905f 100644
--- a/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunner.java
+++ b/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunner.java
@@ -5,6 +5,8 @@
  */
 package org.elasticsearch.xpack.indexlifecycle;
 
+import com.carrotsearch.hppc.cursors.ObjectCursor;
+
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.admin.indices.shrink.ShrinkAction;
@@ -342,6 +344,36 @@ public class IndexLifecycleRunner {
         }
     }
 
+    /**
+     * Returns <code>true</code> if the provided policy is allowed to be updated
+     * given the current {@link ClusterState}. In practice this method checks
+     * that all the indexes using the provided <code>policyName</code> is in a
+     * state where it is able to deal with the policy being updated to
+     * <code>newPolicy</code>. If any of these indexes is not in a state wheree
+     * it can deal with the update the method will return <code>false</code>.
+     * 
+     * @param policyName
+     *            the name of the policy being updated
+     * @param newPolicy
+     *            the new version of the {@link LifecyclePolicy}
+     * @param currentState
+     *            the current {@link ClusterState}
+     */
+    public static boolean canUpdatePolicy(String policyName, LifecyclePolicy newPolicy, ClusterState currentState) {
+        for (ObjectCursor<IndexMetaData> cursor : currentState.getMetaData().indices().values()) {
+            IndexMetaData idxMetadata = cursor.value;
+            Settings idxSettings = idxMetadata.getSettings();
+            String currentPolicyName = LifecycleSettings.LIFECYCLE_NAME_SETTING.get(idxSettings);
+            if (policyName.equals(currentPolicyName)) {
+                StepKey currentStepKey = IndexLifecycleRunner.getCurrentStepKey(idxSettings);
+                if (canSetPolicy(currentStepKey, policyName, newPolicy) == false) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
     public static ClusterState removePolicyForIndexes(final Index[] indices, ClusterState currentState, List<String> failedIndexes) {
         MetaData.Builder newMetadata = MetaData.builder(currentState.getMetaData());
         boolean clusterStateChanged = false;
diff --git a/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/action/TransportPutLifecycleAction.java b/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/action/TransportPutLifecycleAction.java
index b9f9814e9c0..0d1096c6e23 100644
--- a/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/action/TransportPutLifecycleAction.java
+++ b/x-pack/plugin/index-lifecycle/src/main/java/org/elasticsearch/xpack/indexlifecycle/action/TransportPutLifecycleAction.java
@@ -27,6 +27,7 @@ import org.elasticsearch.xpack.core.indexlifecycle.OperationMode;
 import org.elasticsearch.xpack.core.indexlifecycle.action.PutLifecycleAction;
 import org.elasticsearch.xpack.core.indexlifecycle.action.PutLifecycleAction.Request;
 import org.elasticsearch.xpack.core.indexlifecycle.action.PutLifecycleAction.Response;
+import org.elasticsearch.xpack.indexlifecycle.IndexLifecycleRunner;
 
 import java.util.Map;
 import java.util.SortedMap;
@@ -72,7 +73,8 @@ public class TransportPutLifecycleAction extends TransportMasterNodeAction<Reque
                         if (currentMetadata == null) { // first time using index-lifecycle feature, bootstrap metadata
                             currentMetadata = IndexLifecycleMetadata.EMPTY;
                         }
-                        if (currentMetadata.getPolicyMetadatas().containsKey(request.getPolicy().getName())) {
+                        if (currentMetadata.getPolicyMetadatas().containsKey(request.getPolicy().getName()) && IndexLifecycleRunner
+                                .canUpdatePolicy(request.getPolicy().getName(), request.getPolicy(), currentState) == false) {
                             throw new ResourceAlreadyExistsException("Lifecycle policy already exists: {}",
                                     request.getPolicy().getName());
                         }
@@ -95,4 +97,4 @@ public class TransportPutLifecycleAction extends TransportMasterNodeAction<Reque
     protected ClusterBlockException checkBlock(Request request, ClusterState state) {
         return state.blocks().globalBlockedException(ClusterBlockLevel.METADATA_WRITE);
     }
-}
+}
\ No newline at end of file
diff --git a/x-pack/plugin/index-lifecycle/src/test/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunnerTests.java b/x-pack/plugin/index-lifecycle/src/test/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunnerTests.java
index dc833388043..327a7373a9c 100644
--- a/x-pack/plugin/index-lifecycle/src/test/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunnerTests.java
+++ b/x-pack/plugin/index-lifecycle/src/test/java/org/elasticsearch/xpack/indexlifecycle/IndexLifecycleRunnerTests.java
@@ -911,6 +911,162 @@ public class IndexLifecycleRunnerTests extends ESTestCase {
         assertSame(clusterState, newClusterState);
     }
 
+    public void testCanUpdatePolicy() {
+        String indexName = randomAlphaOfLength(10);
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+        StepKey currentStep = AbstractStepTestCase.randomStepKey();
+        Settings.Builder indexSettingsBuilder = Settings.builder().put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName)
+                .put(LifecycleSettings.LIFECYCLE_PHASE, currentStep.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        ClusterState clusterState = buildClusterState(indexName, indexSettingsBuilder);
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertTrue(canUpdatePolicy);
+    }
+
+    public void testCanUpdatePolicyIndexInShrink() {
+        String indexName = randomAlphaOfLength(10);
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+        StepKey currentStep = new StepKey(randomAlphaOfLength(10), ShrinkAction.NAME, randomAlphaOfLength(10));
+        Settings.Builder indexSettingsBuilder = Settings.builder().put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName)
+                .put(LifecycleSettings.LIFECYCLE_PHASE, currentStep.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        ClusterState clusterState = buildClusterState(indexName, indexSettingsBuilder);
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertFalse(canUpdatePolicy);
+    }
+
+    public void testCanUpdatePolicyIndexNotManaged() {
+        String indexName = randomAlphaOfLength(10);
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+        Settings.Builder indexSettingsBuilder = Settings.builder();
+        ClusterState clusterState = buildClusterState(indexName, indexSettingsBuilder);
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertTrue(canUpdatePolicy);
+    }
+
+    public void testCanUpdatePolicyDifferentPolicy() {
+        String indexName = randomAlphaOfLength(10);
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+        StepKey currentStep = new StepKey(randomAlphaOfLength(10), ShrinkAction.NAME, randomAlphaOfLength(10));
+        Settings.Builder indexSettingsBuilder = Settings.builder().put(LifecycleSettings.LIFECYCLE_NAME, "different_policy")
+                .put(LifecycleSettings.LIFECYCLE_PHASE, currentStep.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        ClusterState clusterState = buildClusterState(indexName, indexSettingsBuilder);
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertTrue(canUpdatePolicy);
+    }
+
+    public void testCanUpdatePolicyMultipleIndexesUpdateAllowed() {
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+
+        String index1Name = randomAlphaOfLength(10);
+        StepKey currentStep1 = AbstractStepTestCase.randomStepKey();
+        Settings.Builder indexSettingsBuilder1 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName).put(LifecycleSettings.LIFECYCLE_PHASE, currentStep1.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep1.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep1.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata1 = IndexMetaData.builder(index1Name).settings(indexSettingsBuilder1).build();
+
+        String index2Name = randomAlphaOfLength(10);
+        StepKey currentStep2 = AbstractStepTestCase.randomStepKey();
+        Settings.Builder indexSettingsBuilder2 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName).put(LifecycleSettings.LIFECYCLE_PHASE, currentStep2.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep2.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep2.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata2 = IndexMetaData.builder(index2Name).settings(indexSettingsBuilder2).build();
+
+        String index3Name = randomAlphaOfLength(10);
+        StepKey currentStep3 = new StepKey(randomAlphaOfLength(10), ShrinkAction.NAME, randomAlphaOfLength(10));
+        Settings.Builder indexSettingsBuilder3 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, "different_policy").put(LifecycleSettings.LIFECYCLE_PHASE, currentStep3.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep3.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep3.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata3 = IndexMetaData.builder(index3Name).settings(indexSettingsBuilder3).build();
+
+        String index4Name = randomAlphaOfLength(10);
+        Settings.Builder indexSettingsBuilder4 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT);
+        IndexMetaData indexMetadata4 = IndexMetaData.builder(index4Name).settings(indexSettingsBuilder4).build();
+
+        MetaData metadata = MetaData.builder().put(indexMetadata1, true).put(indexMetadata2, true).put(indexMetadata3, true)
+                .put(indexMetadata4, true).build();
+        ClusterState clusterState = ClusterState.builder(new ClusterName("my_cluster")).metaData(metadata).build();
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertTrue(canUpdatePolicy);
+    }
+
+    public void testCanUpdatePolicyMultipleIndexesUpdateForbidden() {
+        String oldPolicyName = "old_policy";
+        String newPolicyName = "new_policy";
+        LifecyclePolicy newPolicy = new LifecyclePolicy(TestLifecycleType.INSTANCE, newPolicyName, Collections.emptyMap());
+
+        String index1Name = randomAlphaOfLength(10);
+        StepKey currentStep1 = AbstractStepTestCase.randomStepKey();
+        Settings.Builder indexSettingsBuilder1 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName).put(LifecycleSettings.LIFECYCLE_PHASE, currentStep1.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep1.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep1.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata1 = IndexMetaData.builder(index1Name).settings(indexSettingsBuilder1).build();
+
+        String index2Name = randomAlphaOfLength(10);
+        StepKey currentStep2 = new StepKey(randomAlphaOfLength(10), ShrinkAction.NAME, randomAlphaOfLength(10));
+        Settings.Builder indexSettingsBuilder2 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, oldPolicyName).put(LifecycleSettings.LIFECYCLE_PHASE, currentStep2.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep2.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep2.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata2 = IndexMetaData.builder(index2Name).settings(indexSettingsBuilder2).build();
+
+        String index3Name = randomAlphaOfLength(10);
+        StepKey currentStep3 = new StepKey(randomAlphaOfLength(10), ShrinkAction.NAME, randomAlphaOfLength(10));
+        Settings.Builder indexSettingsBuilder3 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(LifecycleSettings.LIFECYCLE_NAME, "different_policy").put(LifecycleSettings.LIFECYCLE_PHASE, currentStep3.getPhase())
+                .put(LifecycleSettings.LIFECYCLE_ACTION, currentStep3.getAction())
+                .put(LifecycleSettings.LIFECYCLE_STEP, currentStep3.getName()).put(LifecycleSettings.LIFECYCLE_SKIP, true);
+        IndexMetaData indexMetadata3 = IndexMetaData.builder(index3Name).settings(indexSettingsBuilder3).build();
+
+        String index4Name = randomAlphaOfLength(10);
+        Settings.Builder indexSettingsBuilder4 = Settings.builder().put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
+                .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 0).put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT);
+        IndexMetaData indexMetadata4 = IndexMetaData.builder(index4Name).settings(indexSettingsBuilder4).build();
+
+        MetaData metadata = MetaData.builder().put(indexMetadata1, true).put(indexMetadata2, true).put(indexMetadata3, true)
+                .put(indexMetadata4, true).build();
+        ClusterState clusterState = ClusterState.builder(new ClusterName("my_cluster")).metaData(metadata).build();
+
+        boolean canUpdatePolicy = IndexLifecycleRunner.canUpdatePolicy(oldPolicyName, newPolicy, clusterState);
+
+        assertFalse(canUpdatePolicy);
+    }
+
     public void testRemovePolicyForIndex() {
         String indexName = randomAlphaOfLength(10);
         String oldPolicyName = "old_policy";
diff --git a/x-pack/plugin/src/test/resources/rest-api-spec/test/index_lifecycle/10_basic.yml b/x-pack/plugin/src/test/resources/rest-api-spec/test/index_lifecycle/10_basic.yml
index 61435af9f5f..c12c2ff6bc7 100644
--- a/x-pack/plugin/src/test/resources/rest-api-spec/test/index_lifecycle/10_basic.yml
+++ b/x-pack/plugin/src/test/resources/rest-api-spec/test/index_lifecycle/10_basic.yml
@@ -61,6 +61,112 @@ setup:
       xpack.index_lifecycle.get_lifecycle:
         lifecycle: "my_timeseries_lifecycle"
 
+---
+"Test Policy Update":
+  - do:
+      acknowlege: true
+      xpack.index_lifecycle.put_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+        body: |
+           {
+             "policy": {
+               "type": "timeseries",
+               "phases": {
+                 "warm": {
+                   "after": "10s",
+                   "actions": {
+                     "forcemerge": {
+                       "max_num_segments": 10000
+                     }
+                   }
+                 },
+                 "delete": {
+                   "after": "30s",
+                   "actions": {
+                     "delete": {}
+                   }
+                 }
+               }
+             }
+           }
+
+  - do:
+      acknowledge: true
+      xpack.index_lifecycle.get_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+  - match: { my_timeseries_lifecycle.type: "timeseries" }
+  - match: { my_timeseries_lifecycle.phases.warm.after: "10s" }
+  - match: { my_timeseries_lifecycle.phases.delete.after: "30s" }
+
+
+  - do:
+      indices.create:
+        index: my_index
+        body:
+          settings:
+            index.lifecycle.name: "my_moveable_timeseries_lifecycle"
+
+  - do:
+      indices.create:
+        index: my_index2
+        body:
+          settings:
+            index.lifecycle.name: "my_moveable_timeseries_lifecycle"
+  
+  - do:
+      acknowlege: true
+      xpack.index_lifecycle.put_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+        body: |
+           {
+             "policy": {
+               "type": "timeseries",
+               "phases": {
+                 "warm": {
+                   "after": "300s",
+                   "actions": {
+                     "forcemerge": {
+                       "max_num_segments": 10000
+                     }
+                   }
+                 },
+                 "delete": {
+                   "after": "600s",
+                   "actions": {
+                     "delete": {}
+                   }
+                 }
+               }
+             }
+           }
+
+  - do:
+      acknowledge: true
+      xpack.index_lifecycle.get_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+  - match: { my_timeseries_lifecycle.type: "timeseries" }
+  - match: { my_timeseries_lifecycle.phases.warm.after: "300s" }
+  - match: { my_timeseries_lifecycle.phases.delete.after: "600s" }
+
+  - do:
+      acknowledge: true
+      indices.delete:
+        index: my_index
+  - do:
+      acknowledge: true
+      indices.delete:
+        index: my_index2
+
+  - do:
+      acknowledge: true
+      xpack.index_lifecycle.delete_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+
+  - do:
+      catch: missing
+      xpack.index_lifecycle.get_lifecycle:
+        lifecycle: "my_timeseries_lifecycle"
+
 ---
 "Test Undeletable Policy In Use":
   - do: