A zoom lens system, includes a first lens unit, a second lens unit, and a third lens unit. The second lens unit is moved to the object side in zooming such that an interval between the first lens unit and the second lens unit at a telephoto end becomes smaller than an interval between the first lens unit and the second lens unit at a wide angle end. The first lens unit includes a first lens element, a second lens element, and a third lens element. The first lens element has an aspherical surface of a shape that the negative refracting power decreases from a lens central portion to a lens peripheral portion. The second lens element is formed in a meniscus shape which is convex on the object side. A refractive index of a material constituting the first and second lens elements is appropriately selected.