Optical motion capture systems have been a popular means for both recording and estimating subject’s movement information including gait speed and joint angles; such information facilitates rehabilitation of patients. However, current optical motion capture systems are usually expensive and thus not affordable. In this study, we have developed and tested a low-cost optical motion capture system utilizing four USB webcams. Shoulder three-dimensional angles of a mannequin was measured by the low-cost motion capture system and precision encoders built-in the mannequin. Maximum of 2° difference between the shoulder angles estimated with the low-cost motion capture system and that from the encoders confirms the feasibility of the low-cost motion capture system.