diff --git a/src/groupdb.js b/src/groupdb.js
index 1f246467d..82690a220 100644
--- a/src/groupdb.js
+++ b/src/groupdb.js
@@ -9,6 +9,7 @@ exports = module.exports = {
     getMembers: getMembers,
     addMember: addMember,
     removeMember: removeMember,
+    isMember: isMember,
 
     _clear: clear
 };
@@ -116,3 +117,15 @@ function removeMember(groupId, userId, callback) {
         callback(null);
     });
 }
+
+function isMember(groupId, userId, callback) {
+    assert.strictEqual(typeof groupId, 'string');
+    assert.strictEqual(typeof userId, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    database.query('SELECT 1 FROM groupMembers WHERE groupId=? AND userId=?', [ groupId, userId ], function (error, result) {
+        if (error) return callback(new DatabaseError(DatabaseError.INTERNAL_ERROR, error));
+
+        callback(null, result.length !== 0);
+    });
+}
diff --git a/src/groups.js b/src/groups.js
index 682398913..f3bb3f645 100644
--- a/src/groups.js
+++ b/src/groups.js
@@ -11,7 +11,8 @@ exports = module.exports = {
 
     getMembers: getMembers,
     addMember: addMember,
-    removeMember: removeMember
+    removeMember: removeMember,
+    isMember: isMember
 };
 
 var assert = require('assert'),
@@ -134,3 +135,16 @@ function removeMember(groupId, userId, callback) {
         return callback(null);
     });
 }
+
+function isMember(groupId, userId, callback) {
+    assert.strictEqual(typeof groupId, 'string');
+    assert.strictEqual(typeof userId, 'string');
+    assert.strictEqual(typeof callback, 'function');
+
+    groupdb.isMember(groupId, userId, function (error, result) {
+        if (error && error.reason === DatabaseError.NOT_FOUND) return callback(new GroupError(GroupError.NOT_FOUND));
+        if (error) return callback(new GroupError(GroupError.INTERNAL_ERROR, error));
+
+        return callback(null, result);
+    });
+}
diff --git a/src/test/group-test.js b/src/test/group-test.js
index a37d21b86..9568caf57 100644
--- a/src/test/group-test.js
+++ b/src/test/group-test.js
@@ -136,6 +136,14 @@ describe('Group membership', function () {
         });
     });
 
+    it('isMember returns false', function (done) {
+        groups.isMember(GROUP_ID, USER_0.id, function (error, member) {
+            expect(error).to.be(null);
+            expect(member).to.be(false);
+            done();
+        });
+    });
+
     it('can add member', function (done) {
         groups.addMember(GROUP_ID, USER_0.id, function (error) {
             expect(error).to.be(null);
@@ -143,6 +151,14 @@ describe('Group membership', function () {
         });
     });
 
+    it('isMember returns true', function (done) {
+        groups.isMember(GROUP_ID, USER_0.id, function (error, member) {
+            expect(error).to.be(null);
+            expect(member).to.be(true);
+            done();
+        });
+    });
+
     it('can get members', function (done) {
         groups.getMembers(GROUP_ID, function (error, result) {
             expect(error).to.be(null);