Heterotopic ossification (HO) is a well-known complication of total hip arthroplasty (THA), especially when the direct lateral approach is used. In this study, we examined the effect of the selective COX-2 inhibitor, celecoxib, on the rates of HO after THA. A control group consisting of 108 patients that did not receive celecoxib was compared with a study group consisting of 106 patients that did receive celecoxib. We assessed the presence and grade of HO using the Brooker classification and Harris hip scores were determined pre- and postoperatively to better quantify clinical outcomes. In this retrospective study of prospectively collected data, celecoxib is associated with a significant reduction in the incidence of HO in patients undergoing THA.