A zoom lens system includes, in order from an object side to an image side, a first lens unit having positive optical power, a second lens unit having negative optical power, and a rear unit including at least one lens unit. During zooming, at least two lens units move so that intervals between the lens units adjacent to each other change. In such a zoom lens system, the second lens unit consists of a negative lens component formed of at least one material and a positive lens element, which are arranged in the stated order from the object side to the image side. A refractive index and an Abbe number of the at least one material forming the negative lens component and a refractive index of a material forming the positive lens element are appropriately set, whereby high optical performance is obtained.