diff --git a/models/action.go b/models/action.go
index b089870c741a7..95ccd7555a8e7 100644
--- a/models/action.go
+++ b/models/action.go
@@ -758,6 +758,8 @@ func CommitRepoAction(opts CommitRepoActionOptions) error {
 	case ActionDeleteBranch: // Delete Branch
 		isHookEventPush = true
 
+		CloseActivePullRequests(pusher, repo, refName)
+
 		if err = PrepareWebhooks(repo, HookEventDelete, &api.DeletePayload{
 			Ref:        refName,
 			RefType:    "branch",
diff --git a/models/fixtures/pull_request.yml b/models/fixtures/pull_request.yml
index d8313f9f90585..989282cb05b99 100644
--- a/models/fixtures/pull_request.yml
+++ b/models/fixtures/pull_request.yml
@@ -22,7 +22,7 @@
   head_repo_id: 1
   base_repo_id: 1
   head_user_name: user1
-  head_branch: branch2
+  head_branch: develop
   base_branch: master
   merge_base: fedcba9876543210
   has_merged: false
diff --git a/models/issue.go b/models/issue.go
index ddc7fa24af8a1..509d21fee7304 100644
--- a/models/issue.go
+++ b/models/issue.go
@@ -1803,6 +1803,15 @@ func (issue *Issue) getBlockingDependencies(e Engine) (issueDeps []*Issue, err e
 		Find(&issueDeps)
 }
 
+// Returns true if the issue has any open issue as its dependency.
+func (issue *Issue) isBlocked(e Engine) (bool, error) {
+	count, err := e.Table("issue_dependency").
+		Join("INNER", "issue", "issue.id = issue_dependency.issue_id").
+		Where("dependency_id = ? AND issue.is_closed = ?", issue.ID, false).
+		Count()
+	return count > 0, err
+}
+
 // BlockedByDependencies finds all Dependencies an issue is blocked by
 func (issue *Issue) BlockedByDependencies() ([]*Issue, error) {
 	return issue.getBlockedByDependencies(x)
@@ -1812,3 +1821,8 @@ func (issue *Issue) BlockedByDependencies() ([]*Issue, error) {
 func (issue *Issue) BlockingDependencies() ([]*Issue, error) {
 	return issue.getBlockingDependencies(x)
 }
+
+// IsBlocked returns true if the issue has any open issue as its dependency.
+func (issue *Issue) IsBlocked() (bool, error) {
+	return issue.isBlocked(x)
+}
diff --git a/models/pull.go b/models/pull.go
index 71a2439b2c335..2378254482664 100644
--- a/models/pull.go
+++ b/models/pull.go
@@ -1527,3 +1527,46 @@ func TestPullRequests() {
 func InitTestPullRequests() {
 	go TestPullRequests()
 }
+
+// CloseActivePullRequests closes the issue of all the active pull requests associated with a branch
+func CloseActivePullRequests(doer *User, repo *Repository, branchName string) {
+	baseprs, err := GetUnmergedPullRequestsByBaseInfo(repo.ID, branchName)
+	if err != nil {
+		log.Error("Find pull requests [base_repo_id: %d, base_branch: %s]: %v", repo.ID, branchName, err)
+		return
+	}
+	headprs, err := GetUnmergedPullRequestsByHeadInfo(repo.ID, branchName)
+	if err != nil {
+		log.Error("Find pull requests [head_repo_id: %d, head_branch: %s]: %v", repo.ID, branchName, err)
+		return
+	}
+	prs := append(baseprs, headprs...)
+	for statusChanged := true; statusChanged; {
+		statusChanged = false
+		for _, pr := range prs {
+			if err = pr.LoadIssue(); err != nil {
+				log.Error("LoadIssue: %v", err)
+			}
+			if pr.Issue.IsClosed {
+				continue
+			}
+			if blocked, err := pr.Issue.IsBlocked(); err != nil {
+				log.Error("IsBlocked: %v", err)
+			} else if !blocked {
+				err = pr.Issue.ChangeStatus(doer, true)
+				if err != nil {
+					log.Error("ChangeStatus: %v", err)
+				} else {
+					log.Trace("Issue [%d] status changed to closed", pr.IssueID)
+					statusChanged = true
+				}
+			}
+		}
+	}
+
+	for _, pr := range prs {
+		if !pr.Issue.IsClosed {
+			log.Warn("Issue [%d] status change blocked by existing dependencies.", pr.Issue.ID)
+		}
+	}
+}
diff --git a/models/pull_test.go b/models/pull_test.go
index 1dad664077711..53611a5389e5d 100644
--- a/models/pull_test.go
+++ b/models/pull_test.go
@@ -90,7 +90,7 @@ func TestPullRequestsOldest(t *testing.T) {
 
 func TestGetUnmergedPullRequest(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
-	pr, err := GetUnmergedPullRequest(1, 1, "branch2", "master")
+	pr, err := GetUnmergedPullRequest(1, 1, "develop", "master")
 	assert.NoError(t, err)
 	assert.Equal(t, int64(2), pr.ID)
 
@@ -101,12 +101,12 @@ func TestGetUnmergedPullRequest(t *testing.T) {
 
 func TestGetUnmergedPullRequestsByHeadInfo(t *testing.T) {
 	assert.NoError(t, PrepareTestDatabase())
-	prs, err := GetUnmergedPullRequestsByHeadInfo(1, "branch2")
+	prs, err := GetUnmergedPullRequestsByHeadInfo(1, "develop")
 	assert.NoError(t, err)
 	assert.Len(t, prs, 1)
 	for _, pr := range prs {
 		assert.Equal(t, int64(1), pr.HeadRepoID)
-		assert.Equal(t, "branch2", pr.HeadBranch)
+		assert.Equal(t, "develop", pr.HeadBranch)
 	}
 }
 
@@ -268,3 +268,77 @@ func TestPullRequest_GetWorkInProgressPrefixWorkInProgress(t *testing.T) {
 	pr.Issue.Title = "[wip] " + original
 	assert.Equal(t, "[wip]", pr.GetWorkInProgressPrefix())
 }
+
+func closeActivePullRequests(t *testing.T, pr *PullRequest, repo *Repository, branchName string) {
+	assert.NoError(t, repo.GetOwner())
+
+	CloseActivePullRequests(repo.Owner, repo, branchName)
+	pr.Issue = nil
+	pr.LoadIssue()
+	assert.Equal(t, true, pr.Issue.IsClosed)
+}
+
+func TestPullRequest_CloseActivePullRequests(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	// Delete head branch.
+	pr := AssertExistsAndLoadBean(t, &PullRequest{ID: 2}).(*PullRequest)
+	pr.GetHeadRepo()
+	closeActivePullRequests(t, pr, pr.HeadRepo, pr.HeadBranch)
+
+	// Reopen pull request.
+	assert.NoError(t, pr.Issue.ChangeStatus(pr.HeadRepo.Owner, false))
+
+	// Delete base branch.
+	pr = AssertExistsAndLoadBean(t, &PullRequest{ID: 2}).(*PullRequest)
+	pr.GetBaseRepo()
+	closeActivePullRequests(t, pr, pr.BaseRepo, pr.BaseBranch)
+}
+
+func createTestPullRequest(t *testing.T, repo *Repository, user *User, baseBranch string, headBranch string) *PullRequest {
+	prIssue := &Issue{
+		RepoID:   repo.ID,
+		Repo:     repo,
+		Title:    "test",
+		PosterID: user.ID,
+		Poster:   user,
+	}
+	pr := &PullRequest{
+		HeadRepoID:   repo.ID,
+		BaseRepoID:   repo.ID,
+		HeadRepo:     repo,
+		BaseRepo:     repo,
+		HeadUserName: user.Name,
+		HeadBranch:   headBranch,
+		BaseBranch:   baseBranch,
+		Type:         PullRequestGitea,
+	}
+	labelIDs := make([]int64, 0)
+	uuids := make([]string, 0)
+	patch := make([]byte, 0)
+	assigneeIDs := make([]int64, 0)
+	err := NewPullRequest(repo, prIssue, labelIDs, uuids, pr, patch, assigneeIDs)
+	assert.NoError(t, err)
+	return pr
+}
+
+func TestPullRequest_CloseActivePullRequestsDependent(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	// Create a test pull request.
+	repo := AssertExistsAndLoadBean(t, &Repository{ID: 1}).(*Repository)
+	user := AssertExistsAndLoadBean(t, &User{ID: 1}).(*User)
+	pr1 := AssertExistsAndLoadBean(t, &PullRequest{ID: 2}).(*PullRequest)
+	pr2 := createTestPullRequest(t, repo, user, "develop", "master")
+	pr1.LoadIssue()
+	pr2.LoadIssue()
+
+	// Add a dependency from pr2 to pr1.
+	err := CreateIssueDependency(user, pr2.Issue, pr1.Issue)
+	assert.NoError(t, err)
+
+	closeActivePullRequests(t, pr2, pr2.BaseRepo, pr2.BaseBranch)
+	pr1.Issue = nil
+	pr1.LoadIssue()
+	assert.Equal(t, true, pr1.Issue.IsClosed)
+}