There is concern about safety of bilateral total hip arthroplasty (THA).This study aims to compare in-hospital complication rates between unilateral, simultaneous and staged bilateral THAs. The Nationwide Inpatient Sample from 2002–2010 was used. Patients and complications were identified using ICD-9-CM codes. In multivariate analysis, bilateral THA had higher risk of systemic complications (Odds ratio (OR): 2.1, P < 0.001) compared to unilateral procedure, whereas no significant difference existed between simultaneous and staged bilateral THAs. The rate of local complications was higher in bilateral versus unilateral (4.96% versus 4.54%, P = 0.009) and in staged versus simultaneous bilateral THAs (OR: 1.75, P = 0.05). Bilateral THA increases risk of systemic complications compared to unilateral surgery and simultaneous bilateral THA appears to be safer than staging during one hospitalization.