OBJECTIVES: To determine risk factors for early conversion total hip arthroplasty (THA) after operative treatment of acetabular fractures. DESIGN: Retrospective cohort. SETTING: Level I trauma center. PATIENTS AND INTERVENTION: We reviewed 685 operative acetabular fractures at our institution from 2011 to 2017, with a median follow-up of 12 months (range, 4-105 months). MAIN OUTCOME MEASURE: Multivariable regression analysis was performed after univariate analysis to identify independent risk factors for conversion THA. Sensitivity analysis was performed with minimum follow-up set at 6 and 12 months. RESULTS: One hundred eight patients (16%) underwent conversion THA, with 52% of conversions occurring within 1 year, an additional 27% within 2 years, and the remaining 21% within 6 years of the index acetabular open reduction internal fixation. The median time to conversion THA was 11.5 months (range, 0.5-72 months). The risk of conversion THA by fracture pattern was 53 of 196 (27%) for transverse posterior wall (TPW), 12 of 52 (23%) for T shaped, 10 of 68 (15%) for posterior column with posterior wall, and 25 of 207 (12%) for posterior wall. Independent risk factors for early conversion included the following: TPW fracture, protrusio, hip dislocation, increased body mass index, increased age, infection, and dislocation after open reduction internal fixation. Independent risk factors for early conversion THA specific to patients with TPW fractures include only increased age and body mass index. Sensitivity analysis showed no change in results using either 6 or 12-month minimum follow-up. CONCLUSION: Transverse posterior wall fractures have a high risk of early conversion THA compared with other acetabular fracture patterns, especially when in combination with other significant risk factors. Consideration for different and novel management options warrants further study in this subset of acetabular fracture patients. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.