A zoom lens includes a fixing barrel, a cam barrel, a guide barrel, a first lens group, a second lens group, and a third lens group. The cam barrel is rotatably received in the fixing barrel. The guiding barrel is movably received in the fixing barrel and partially receives the cam barrel. The guiding barrel is moveable along an optical axis of the zoom lens following the motion of the cam barrel. The first lens group is rotatably received in the guiding barrel. The second lens group is rotatably received in the cam barrel. The first and second lens groups move along the optical axis following the rotation of the cam barrel. The third lens group is aligned with the first and second lens groups, and driven by a driver to be movably received in the fixing barrel and moveable along the optical axis of the zoom lens.