diff --git a/dev-infra/ng-dev.js b/dev-infra/ng-dev.js
index d5214b1940..d20c1495ff 100755
--- a/dev-infra/ng-dev.js
+++ b/dev-infra/ng-dev.js
@@ -3379,6 +3379,15 @@ var PullRequestFailure = /** @class */ (function () {
     PullRequestFailure.notMergeReady = function () {
         return new this("Not marked as merge ready.");
     };
+    PullRequestFailure.isDraft = function () {
+        return new this('Pull request is still in draft.');
+    };
+    PullRequestFailure.isClosed = function () {
+        return new this('Pull request is already closed.');
+    };
+    PullRequestFailure.isMerged = function () {
+        return new this('Pull request is already merged.');
+    };
     PullRequestFailure.mismatchingTargetBranch = function (allowedBranches) {
         return new this("Pull request is set to wrong base branch. Please update the PR in the Github UI " +
             ("to one of the following branches: " + allowedBranches.join(', ') + "."));
@@ -3490,6 +3499,7 @@ function loadAndValidatePullRequest(_a, prNumber, ignoreNonFatalFailures) {
                     }
                     commitsInPr = prData.commits.nodes.map(function (n) { return parseCommitMessage(n.commit.message); });
                     try {
+                        assertPendingState(prData);
                         assertChangesAllowForTargetLabel(commitsInPr, targetLabel, config);
                         assertCorrectBreakingChangeLabeling(commitsInPr, labels, config);
                     }
@@ -3541,6 +3551,8 @@ function loadAndValidatePullRequest(_a, prNumber, ignoreNonFatalFailures) {
 /* Graphql schema for the response body the requested pull request. */
 var PR_SCHEMA$2 = {
     url: typedGraphqlify.types.string,
+    isDraft: typedGraphqlify.types.boolean,
+    state: typedGraphqlify.types.oneOf(['OPEN', 'MERGED', 'CLOSED']),
     number: typedGraphqlify.types.number,
     // Only the last 100 commits from a pull request are obtained as we likely will never see a pull
     // requests with more than 100 commits.
@@ -3646,6 +3658,18 @@ function assertCorrectBreakingChangeLabeling(commits, labels, config) {
         throw PullRequestFailure.missingBreakingChangeCommit();
     }
 }
+/** Assert the pull request is pending, not closed, merged or in draft. */
+function assertPendingState(pr) {
+    if (pr.isDraft) {
+        throw PullRequestFailure.isDraft();
+    }
+    switch (pr.state) {
+        case 'CLOSED':
+            throw PullRequestFailure.isClosed();
+        case 'MERGED':
+            throw PullRequestFailure.isMerged();
+    }
+}
 
 /**
  * @license
diff --git a/dev-infra/pr/merge/failures.ts b/dev-infra/pr/merge/failures.ts
index 5675eb5ad0..587892c8b3 100644
--- a/dev-infra/pr/merge/failures.ts
+++ b/dev-infra/pr/merge/failures.ts
@@ -36,6 +36,18 @@ export class PullRequestFailure {
     return new this(`Not marked as merge ready.`);
   }
 
+  static isDraft() {
+    return new this('Pull request is still in draft.');
+  }
+
+  static isClosed() {
+    return new this('Pull request is already closed.');
+  }
+
+  static isMerged() {
+    return new this('Pull request is already merged.');
+  }
+
   static mismatchingTargetBranch(allowedBranches: string[]) {
     return new this(
         `Pull request is set to wrong base branch. Please update the PR in the Github UI ` +
diff --git a/dev-infra/pr/merge/pull-request.ts b/dev-infra/pr/merge/pull-request.ts
index ea38f4c4d0..b7986269eb 100644
--- a/dev-infra/pr/merge/pull-request.ts
+++ b/dev-infra/pr/merge/pull-request.ts
@@ -82,6 +82,7 @@ export async function loadAndValidatePullRequest(
   const commitsInPr = prData.commits.nodes.map(n => parseCommitMessage(n.commit.message));
 
   try {
+    assertPendingState(prData);
     assertChangesAllowForTargetLabel(commitsInPr, targetLabel, config);
     assertCorrectBreakingChangeLabeling(commitsInPr, labels, config);
   } catch (error) {
@@ -136,6 +137,8 @@ export async function loadAndValidatePullRequest(
 /* Graphql schema for the response body the requested pull request. */
 const PR_SCHEMA = {
   url: graphqlTypes.string,
+  isDraft: graphqlTypes.boolean,
+  state: graphqlTypes.oneOf(['OPEN', 'MERGED', 'CLOSED'] as const),
   number: graphqlTypes.number,
   // Only the last 100 commits from a pull request are obtained as we likely will never see a pull
   // requests with more than 100 commits.
@@ -159,11 +162,13 @@ const PR_SCHEMA = {
   }),
 };
 
+/** A pull request retrieved from github via the graphql API. */
+type RawPullRequest = typeof PR_SCHEMA;
 
 
 /** Fetches a pull request from Github. Returns null if an error occurred. */
 async function fetchPullRequestFromGithub(
-    git: GitClient<true>, prNumber: number): Promise<typeof PR_SCHEMA|null> {
+    git: GitClient<true>, prNumber: number): Promise<RawPullRequest|null> {
   try {
     const x = await getPr(PR_SCHEMA, prNumber, git);
     return x;
@@ -241,3 +246,17 @@ function assertCorrectBreakingChangeLabeling(
     throw PullRequestFailure.missingBreakingChangeCommit();
   }
 }
+
+
+/** Assert the pull request is pending, not closed, merged or in draft. */
+function assertPendingState(pr: RawPullRequest) {
+  if (pr.isDraft) {
+    throw PullRequestFailure.isDraft();
+  }
+  switch (pr.state) {
+    case 'CLOSED':
+      throw PullRequestFailure.isClosed();
+    case 'MERGED':
+      throw PullRequestFailure.isMerged();
+  }
+}