This study addresses the problem of scheduling double-gripper gantry robots and provides a structure for analyzing scheduling problems in a tightly-coupled automated serial production line with deterministic processing time. Literature to date indicates that there has been no documented effort dealing with the scheduling problem of double-gripper gantry robots. This paper presents an optimal schedule by analyzing the cycle time formula for two-station (m=2) tightly-coupled production lines served by a double-gripper gantry robot. The result is then generalized to the problem of scheduling a gantry robot in a production line with m (where m>2) workstations, and finally an optimal schedule for the m-station case is developed. The effectiveness of using double-gripper gantry robots is discussed and some analytical insights into the employment of double-gripper gantry robot are provided for manufacturing system designers.