An adjustable fit insole system for shoes includes an insole member formed of flexible, resilient cushioning material that is removably inserted within the foot-receiving chamber of the shoe, the insole member and the shoe having corresponding heel, arch, ball and toe portions. In order to vary the internal width and girth dimensions of the ball portion of the chamber, a width adjustment pad of a desired thickness and/or hardness is removably connected with the bottom surface of the ball portion of the insole member, thereby to permit the user to customize the fit of the shoe. The top surface of the insole member is contoured to position the foot relative to the insole, and the bottom surface of the heel portion of the insole member is provided with an anti-slip stabilizing arrangement, thereby to prevent sliding movement of the insole member relative to the shoe.