diff --git a/extensions/git/src/commands.ts b/extensions/git/src/commands.ts
index 15532bfc28b..e8c155102a3 100644
--- a/extensions/git/src/commands.ts
+++ b/extensions/git/src/commands.ts
@@ -62,21 +62,18 @@ class CheckoutRemoteHeadItem extends CheckoutItem {
 
 class BranchDeleteItem implements QuickPickItem {
 
-	protected get shortCommit(): string { return (this.ref.commit || '').substr(0, 8); }
-	protected get treeish(): string | undefined { return this.ref.name; }
-	get label(): string { return this.ref.name || this.shortCommit; }
+	private get shortCommit(): string { return (this.ref.commit || '').substr(0, 8); }
+	get branchName(): string | undefined { return this.ref.name; }
+	get label(): string { return this.branchName || ''; }
 	get description(): string { return this.shortCommit; }
 
-	constructor(protected ref: Ref) { }
+	constructor(private ref: Ref) { }
 
-	async run(model: Model): Promise<void> {
-		const ref = this.treeish;
-
-		if (!ref) {
+	async run(model: Model, force?: boolean): Promise<void> {
+		if (!this.branchName) {
 			return;
 		}
-
-		await model.deleteBranch(ref);
+		await model.deleteBranch(this.branchName, force);
 	}
 }
 
@@ -720,22 +717,40 @@ export class CommandCenter {
 	}
 
 	@command('git.deleteBranch')
-	async deleteBranch(branchName: string): Promise<void> {
-		if (typeof branchName === 'string') {
-			return await this.model.deleteBranch(branchName);
-		}
-		const currentHead = this.model.HEAD && this.model.HEAD.name;
-		const heads = this.model.refs.filter(ref => ref.type === RefType.Head && ref.name !== currentHead)
-			.map(ref => new BranchDeleteItem(ref));
+	async deleteBranch(name: string, force?: boolean): Promise<void> {
+		let run: (force?: boolean) => Promise<void>;
+		if (typeof name === 'string') {
+			run = force => this.model.deleteBranch(name, force);
+		} else {
+			const currentHead = this.model.HEAD && this.model.HEAD.name;
+			const heads = this.model.refs.filter(ref => ref.type === RefType.Head && ref.name !== currentHead)
+				.map(ref => new BranchDeleteItem(ref));
 
-		const placeHolder = 'Select a branch to delete';
-		const choice = await window.showQuickPick<BranchDeleteItem>(heads, { placeHolder });
+			const placeHolder = 'Select a branch to delete';
+			const choice = await window.showQuickPick<BranchDeleteItem>(heads, { placeHolder });
 
-		if (!choice) {
-			return;
+			if (!choice) {
+				return;
+			}
+			name = choice.branchName || '';
+			run = force => choice.run(this.model, force);
 		}
 
-		await choice.run(this.model);
+		try {
+			await run(force);
+		} catch (err) {
+			if (err.gitErrorCode !== GitErrorCodes.BranchNotFullyMerged) {
+				throw err;
+			}
+
+			const message = localize('confirm force delete branch', "The branch '{0}' is not fully merged. Delete anyway?", name);
+			const yes = localize('delete branch', "Delete Branch");
+			const pick = await window.showWarningMessage(message, yes);
+
+			if (pick === yes) {
+				await run(true);
+			}
+		}
 	}
 
 	@command('git.pull')
diff --git a/extensions/git/src/git.ts b/extensions/git/src/git.ts
index edba69ad2ed..9ef482def93 100644
--- a/extensions/git/src/git.ts
+++ b/extensions/git/src/git.ts
@@ -273,7 +273,8 @@ export const GitErrorCodes = {
 	CantCreatePipe: 'CantCreatePipe',
 	CantAccessRemote: 'CantAccessRemote',
 	RepositoryNotFound: 'RepositoryNotFound',
-	RepositoryIsLocked: 'RepositoryIsLocked'
+	RepositoryIsLocked: 'RepositoryIsLocked',
+	BranchNotFullyMerged: 'BranchNotFullyMerged'
 };
 
 function getGitErrorCode(stderr: string): string | undefined {
@@ -291,6 +292,8 @@ function getGitErrorCode(stderr: string): string | undefined {
 		return GitErrorCodes.RepositoryNotFound;
 	} else if (/unable to access/.test(stderr)) {
 		return GitErrorCodes.CantAccessRemote;
+	} else if (/branch '.+' is not fully merged/.test(stderr)) {
+		return GitErrorCodes.BranchNotFullyMerged;
 	}
 
 	return void 0;
@@ -650,8 +653,8 @@ export class Repository {
 		await this.run(args);
 	}
 
-	async deleteBranch(name: string): Promise<void> {
-		const args = ['branch', '-d', name];
+	async deleteBranch(name: string, force?: boolean): Promise<void> {
+		const args = ['branch', force ? '-D' : '-d', name];
 		await this.run(args);
 	}
 
diff --git a/extensions/git/src/model.ts b/extensions/git/src/model.ts
index 1ce7f8287a9..aba4a4251d6 100644
--- a/extensions/git/src/model.ts
+++ b/extensions/git/src/model.ts
@@ -454,8 +454,8 @@ export class Model implements Disposable {
 		await this.run(Operation.Branch, () => this.repository.branch(name, true));
 	}
 
-	async deleteBranch(name: string): Promise<void> {
-		await this.run(Operation.DeleteBranch, () => this.repository.deleteBranch(name));
+	async deleteBranch(name: string, force?: boolean): Promise<void> {
+		await this.run(Operation.DeleteBranch, () => this.repository.deleteBranch(name, force));
 	}
 
 	async checkout(treeish: string): Promise<void> {