diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/ProcessGroupResource.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/ProcessGroupResource.java
index 93416a20ba..0ececa1273 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/ProcessGroupResource.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/api/ProcessGroupResource.java
@@ -35,6 +35,7 @@ import org.apache.nifi.authorization.user.NiFiUserUtils;
 import org.apache.nifi.cluster.protocol.NodeIdentifier;
 import org.apache.nifi.controller.Snippet;
 import org.apache.nifi.web.NiFiServiceFacade;
+import org.apache.nifi.web.ResourceNotFoundException;
 import org.apache.nifi.web.Revision;
 import org.apache.nifi.web.api.dto.ConnectionDTO;
 import org.apache.nifi.web.api.dto.ProcessGroupDTO;
@@ -109,8 +110,6 @@ public class ProcessGroupResource extends ApplicationResource {
 
     private static final Logger logger = LoggerFactory.getLogger(ProcessGroupResource.class);
 
-    private static final String VERBOSE = "false";
-
     @Context
     private ResourceContext resourceContext;
 
@@ -1530,10 +1529,17 @@ public class ProcessGroupResource extends ApplicationResource {
 
                 // ensure write access to the source
                 final Authorizable source = lookup.getConnectable(connection.getSource().getId());
+                if (source == null) {
+                    throw new ResourceNotFoundException("Cannot find source component with ID [" + connection.getSource().getId() + "]");
+                }
                 source.authorize(authorizer, RequestAction.WRITE, NiFiUserUtils.getNiFiUser());
 
                 // ensure write access to the destination
                 final Authorizable destination = lookup.getConnectable(connection.getDestination().getId());
+                if (destination == null) {
+                    throw new ResourceNotFoundException("Cannot find destination component with ID [" + connection.getDestination().getId() + "]");
+                }
+
                 destination.authorize(authorizer, RequestAction.WRITE, NiFiUserUtils.getNiFiUser());
             });
         }
diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardConnectionDAO.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardConnectionDAO.java
index 16cf03f8d7..7fc09da061 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardConnectionDAO.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/dao/impl/StandardConnectionDAO.java
@@ -378,6 +378,34 @@ public class StandardConnectionDAO extends ComponentDAO implements ConnectionDAO
         if (!validationErrors.isEmpty()) {
             throw new ValidationException(validationErrors);
         }
+
+        // Ensure that both the source and the destination for the connection exist.
+        // In the case that the source or destination is a port in a Remote Process Group,
+        // this is necessary because the ports can change in the background. It may still be
+        // possible for a port to disappear between the 'verify' stage and the creation stage,
+        // but this prevents the case where some nodes already know about the port while other
+        // nodes in the cluster do not. This is a more common case, as users may try to connect
+        // to the port as soon as the port is created.
+        final ConnectableDTO sourceDto = connectionDTO.getSource();
+        if (sourceDto == null || sourceDto.getId() == null) {
+            throw new IllegalArgumentException("Cannot create connection without specifying source");
+        }
+
+        final ConnectableDTO destinationDto = connectionDTO.getDestination();
+        if (destinationDto == null || destinationDto.getId() == null) {
+            throw new IllegalArgumentException("Cannot create connection without specifying destination");
+        }
+
+        final ProcessGroup rootGroup = flowController.getGroup(flowController.getRootGroupId());
+        final Connectable sourceConnectable = rootGroup.findConnectable(sourceDto.getId());
+        if (sourceConnectable == null) {
+            throw new IllegalArgumentException("The specified source for the connection does not exist");
+        }
+
+        final Connectable destinationConnectable = rootGroup.findConnectable(destinationDto.getId());
+        if (destinationConnectable == null) {
+            throw new IllegalArgumentException("The specified destination for the connection does not exist");
+        }
     }
 
     private void verifyList(final FlowFileQueue queue) {