Disclosed is a zoom lens system in which a first lens unit having negative optical power and a second lens unit having positive optical power are arranged in the stated order from an object side to an image side, and in which an interval between the first lens unit and the second lens unit changes in zooming. In such a zoom lens system, the first lens unit includes a first lens component having negative optical power, a second lens component joined to a lens surface of the first lens component, and a third lens component having positive optical power so as to provide the zoom lens system having excellent optical performance by appropriately setting a material forming the first lens component.