A telescoping pier foundation system (100, 100a, 100b) comprises generally an outer shell preferably made of a tough material, such as, a suitable polymer or a metal alloy, having an internal cavity (12) for receiving cementitious mixture. The outer shell comprises a stationary portion (10) and at least one longitudinally telescoping member (30) in longitudinal alignment with one another and connected to one another to achieve a given height, length or depth for forming a pier foundation. After the at least one telescoping member (30) is raised to meet a structural member (80, 80a) of a building and secured to the structural member, the internal cavity (12) of the outer shell is filled with cementitious mixture and cured to form a composite pier foundation.