A zoom lens system includes, in order from an object side to an image side, a first positive lens group (G1), a second negative lens group (G2), a third positive lens group (G3), and a fourth positive lens group (G4). The second and third lens groups are movable for varying the focal length. The zoom lens system offers a four-times zoom ratio, and employs two plastic aspheric lenses (L3, L9) and a resin hybrid lens (L6). The first lens group consists of two lenses (L1, L2) arranged in an abutting relationship. The second and third lens groups each includes a pair of cemented lenses (L4, L5; L7, L8).