Abstract: A zoom lens system comprising, in the order from the object side, a first lens unit which has positive refractive power, a second lens unit which has negative refractive power and is movable along the optical axis for varying focal length, a third lens unit which has negative refractive power and is movable along the optical axis for varying focal length but in a locus different from that of the second lens unit, and a fourth lens unit which has positive refractive power and is always kept fixed, the first lens unit consisting of a negative meniscus lens element convex on the object side and a positive lens element, the second lens unit consisting only of a single negative meniscus lens element convex on the object side, and the third lens unit consisting of a negative lens element and a positive lens element.