diff --git a/git/git.go b/git/git.go
index 9a9c4b76d..684b00c10 100644
--- a/git/git.go
+++ b/git/git.go
@@ -180,6 +180,33 @@ func Commits(baseRef, headRef string) ([]*Commit, error) {
 	return commits, nil
 }
 
+func LastCommit() (*Commit, error) {
+	logCmd, err := GitCommand("-c", "log.ShowSignature=false", "log", "--pretty=format:%H,%s", "-1")
+	if err != nil {
+		return nil, err
+	}
+
+	output, err := run.PrepareCmd(logCmd).Output()
+	if err != nil {
+		return nil, err
+	}
+
+	lines := outputLines(output)
+	if len(lines) != 1 {
+		return nil, ErrNotOnAnyBranch
+	}
+
+	split := strings.SplitN(lines[0], ",", 2)
+	if len(split) != 2 {
+		return nil, ErrNotOnAnyBranch
+	}
+
+	return &Commit{
+		Sha:   split[0],
+		Title: split[1],
+	}, nil
+}
+
 func CommitBody(sha string) (string, error) {
 	showCmd, err := GitCommand("-c", "log.ShowSignature=false", "show", "-s", "--pretty=format:%b", sha)
 	if err != nil {
diff --git a/pkg/cmd/pr/merge/merge.go b/pkg/cmd/pr/merge/merge.go
index 6626c3bc1..4c8c946c0 100644
--- a/pkg/cmd/pr/merge/merge.go
+++ b/pkg/cmd/pr/merge/merge.go
@@ -131,6 +131,16 @@ func mergeRun(opts *MergeOptions) error {
 		return err
 	}
 
+	if opts.SelectorArg == "" {
+		localBranchLastCommit, err := git.LastCommit()
+		if err == nil {
+			if localBranchLastCommit.Sha != pr.Commits.Nodes[0].Commit.Oid {
+				fmt.Fprintf(opts.IO.ErrOut,
+					"%s Pull request #%d (%s) has diverged from local branch\n", cs.Yellow("!"), pr.Number, pr.Title)
+			}
+		}
+	}
+
 	if pr.Mergeable == "CONFLICTING" {
 		fmt.Fprintf(opts.IO.ErrOut, "%s Pull request #%d (%s) has conflicts and isn't mergeable\n", cs.Red("!"), pr.Number, pr.Title)
 		return cmdutil.SilentError
diff --git a/pkg/cmd/pr/merge/merge_test.go b/pkg/cmd/pr/merge/merge_test.go
index 0f97a945e..ce772f1e6 100644
--- a/pkg/cmd/pr/merge/merge_test.go
+++ b/pkg/cmd/pr/merge/merge_test.go
@@ -336,6 +336,7 @@ func TestPrMerge_deleteBranch(t *testing.T) {
 	cs, cmdTeardown := run.Stub()
 	defer cmdTeardown(t)
 
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "")
 	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
 	cs.Register(`git checkout master`, 0, "")
 	cs.Register(`git rev-parse --verify refs/heads/blueberries`, 0, "")
@@ -401,6 +402,7 @@ func TestPrMerge_noPrNumberGiven(t *testing.T) {
 	cs, cmdTeardown := run.Stub()
 	defer cmdTeardown(t)
 
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "")
 	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
 
 	output, err := runCommand(http, "blueberries", true, "pr merge --merge")
@@ -415,6 +417,39 @@ func TestPrMerge_noPrNumberGiven(t *testing.T) {
 	}
 }
 
+func Test_divergingPullRequestWarning(t *testing.T) {
+	http := initFakeHTTP()
+	defer http.Verify(t)
+	http.Register(
+		httpmock.GraphQL(`query PullRequestForBranch\b`),
+		// FIXME: references fixture from another package
+		httpmock.FileResponse("../view/fixtures/prViewPreviewWithMetadataByBranch.json"))
+	http.Register(
+		httpmock.GraphQL(`mutation PullRequestMerge\b`),
+		httpmock.GraphQLMutation(`{}`, func(input map[string]interface{}) {
+			assert.Equal(t, "PR_10", input["pullRequestId"].(string))
+			assert.Equal(t, "MERGE", input["mergeMethod"].(string))
+			assert.NotContains(t, input, "commitHeadline")
+		}))
+
+	cs, cmdTeardown := run.Stub()
+	defer cmdTeardown(t)
+
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "deadbeef,title")
+	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
+
+	output, err := runCommand(http, "blueberries", true, "pr merge --merge")
+	if err != nil {
+		t.Fatalf("error running command `pr merge`: %v", err)
+	}
+
+	r := regexp.MustCompile(`. Pull request #10 \(Blueberries are a good fruit\) has diverged from local branch\n. Merged pull request #10 \(Blueberries are a good fruit\)\n`)
+
+	if !r.MatchString(output.Stderr()) {
+		t.Fatalf("output did not match regexp /%s/\n> output\n%q\n", r, output.Stderr())
+	}
+}
+
 func TestPrMerge_rebase(t *testing.T) {
 	http := initFakeHTTP()
 	defer http.Verify(t)
@@ -582,6 +617,7 @@ func TestPRMerge_interactive(t *testing.T) {
 	cs, cmdTeardown := run.Stub()
 	defer cmdTeardown(t)
 
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "")
 	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
 	cs.Register(`git checkout master`, 0, "")
 	cs.Register(`git rev-parse --verify refs/heads/blueberries`, 0, "")
@@ -637,6 +673,7 @@ func TestPRMerge_interactiveWithDeleteBranch(t *testing.T) {
 	cs, cmdTeardown := run.Stub()
 	defer cmdTeardown(t)
 
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "")
 	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
 	cs.Register(`git checkout master`, 0, "")
 	cs.Register(`git rev-parse --verify refs/heads/blueberries`, 0, "")
@@ -681,6 +718,7 @@ func TestPRMerge_interactiveCancelled(t *testing.T) {
 	cs, cmdTeardown := run.Stub()
 	defer cmdTeardown(t)
 
+	cs.Register("git -c log.ShowSignature=false log --pretty=format:%H,%s -1", 0, "")
 	cs.Register(`git config --get-regexp.+branch\\\.blueberries\\\.`, 0, "")
 
 	as, surveyTeardown := prompt.InitAskStubber()
diff --git a/pkg/cmd/pr/view/fixtures/prViewPreviewWithMetadataByBranch.json b/pkg/cmd/pr/view/fixtures/prViewPreviewWithMetadataByBranch.json
index 73a64ca1c..15842a7b9 100644
--- a/pkg/cmd/pr/view/fixtures/prViewPreviewWithMetadataByBranch.json
+++ b/pkg/cmd/pr/view/fixtures/prViewPreviewWithMetadataByBranch.json
@@ -116,6 +116,13 @@
               "login": "OWNER"
             },
             "commits": {
+              "nodes": [
+                {
+                  "commit": {
+                    "oid": "123456789"
+                  }
+                }
+              ],
               "totalCount": 8
             },
             "isCrossRepository": false,
@@ -125,4 +132,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}