A zooming mechanism for a zoom lens comprises a zooming frame disposed for translation back and forth with respect to a stationary member in the direction of an optical axis and carrying a focus lens group in a manner to permit its focus adjustment; a drive for translating the zooming frame in the direction of the optical axis, a carrier frame for carrying another zoom lens group and supported within the zooming frame by a support member located therein for translation back and forth in the direction of the optical axis, a device for deriving a rotational drive in association with the translation of the zooming frame in the direction of the optical axis, and a device responsive to the rotational drive to cause a non-linear movement of the carrier frame. A rotational drive is derived in association with the translation of the zooming frame in the direction of the optical axis, and utilized by said non-linear moving device to cause a non-linear movement of the carrier frame to achieve a zooming operation.