Heterotopic ossification (HO) is prevalent after total hip arthroplasty (THA). Oral nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 (COX-2) inhibitors have reduced the incidence of HO; however, to the authors’ knowledge, no studies have reported the incidence and severity of HO with a pain protocol highlighted by celecoxib in the pre- and postoperative period with a posterolateral approach. Between October 2014 and October 2015, a retrospective study was conducted of 687 consecutive primary THAs with minimum 1-year follow-up performed between January 2009 and December 2013. All patients underwent a posterolateral THA with a multimodal pain protocol consisting of preoperative celecoxib; local steroid infiltration intraoperatively; postoperative celecoxib, dexamethasone, and ketorolac; and aspirin or warfarin thromboprophylaxis. For all patients, pre- and postoperative radiographs were examined and classified for HO using the Brooker classification. Interobserver reliability was calculated for both incidence of HO and Brooker classification. Overall, HO was present around 98 (14.3%) THAs. The incidence of Brooker I, II, and III HO was 38 (5.5%), 47 (6.8%), and 12 (1.7%), respectively. No patients required surgical excision or had radiographic evidence of Brooker IV HO. Multivariate logistic regression identified male sex and hypertrophic osteoarthritis as significant risk factors. The use of aspirin for thromboprophylaxis significantly reduced the incidence of HO. This study found the overall incidence of HO when using celecoxib during a posterior THA to be 14.3%, which is similar to what others have reported with the direct lateral approach and with other COX-2 inhibitors for a posterior approach. Risk factors include male sex and preoperative hypertrophic osteoarthritis. [Orthopedics. 2018; 41(1):e92–e97.]