A zoom lens system, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit; and at least one subsequent lens unit, wherein the subsequent lens unit(s) includes a lens unit having negative optical power, the first lens unit is composed of two or less lens elements, the third lens unit is composed of four or more lens elements, the first lens unit and the second lens unit move along an optical axis in zooming, and the condition: 0