A zoom lens system includes, in order from an object side to an image side: a first lens group having positive power; a second lens group having negative power; a third lens group having positive power; a fourth lens group having negative power; a fifth lens group having positive power; and a sixth lens group having power. During zooming from wide angle extremity to telephoto extremity, the distance between respective lens groups changes. The fifth lens group is composed of at most two lens elements, at least one of which is a concave meniscus lens element having a convex surface facing the object side.