A zoom lens assembly comprises an optical system containing lens units arranged on the optical axis, a stationary cylindrical member, and an operation member movable relative to the stationary cylindrical member. The operation member is moved in the direction along the optical axis for zooming and is rotated about the optical axis for focusing. The zoom lens assembly further comprises a lens holder axially movable relative to the stationary cylindrical member and holding a certain lens unit selected from the lens units and a cam member mounted axially movable along the optical axis and rotatable about the optical axis relative to the stationary cylindrical member. The cam member is disposed between the operation member and the lens holder and has a cam connection so formed that when the cam member is rotated about the optical axis, the lens holder is moved in the direction along the optical axis and when the cam member is axially moved, the lens holder is moved together with the cam member in the direction along the optical axis. The zoom lens assembly further comprises interlocking elements for rotating the cam member about the optical axis during the time of the operation member being moved in the direction along the optical axis and for moving the cam member in the direction along the optical axis during the time of the operation member being rotated about the optical axis.