The conversion from a fused hip to conventional total hip arthroplasty (THA) in patients with ankylosing spondylitis can be challenging. The problems are related to patient positioning, surgical exposure, femoral neck osteotomy, identifying the true acetabulum, and proper implant positioning. This case series describes our experience using the Mako Robotic-Arm in four bilateral THA procedures (each conducted in a single session) and one unilateral procedure in a fifth patient. Robotic total hip arthroplasty (RTHA) simplified THA by providing real-time information on the relative positions of the femur, pelvis, instruments, and implants to guide the surgery and implant placement.