To obtain a small-sized zoom lens system being a telephoto type three-group zoom lens and whose zoom ratio is about 3.5.

As for the zoom lens system which is constituted of a 1st negative lens group, a 2nd positive lens group and a 3rd negative lens group in order from an object side, and for zooming by moving the three lens groups, that is, the 1st lens group to the 3rd lens group, in an optical axis direction, the following conditional expressions (1) and (2) are satisfied; (1) 0.03<(dW12-dT12/fW<0.1 and (2) -4<fT/f1G<-2 Provided that dW12 denotes a distance between the surface closest to the image side of the 1st lens group and the surface closest to the object side of the 2nd lens group at a short focal distance end, dT12 denotes a distance between the surface closest to the image side of the 1st lens group and the surface closest to the object side of the 2nd lens group at a long focal distance side, fW denotes the focal distance of the whole system at the short focal distance side, fT denotes the focal distance of the whole system at the long focal distance side, and f1G denotes the focal distance of the 1st negative lens group.