© 2019, American College of Rheumatology Objective: Guidelines recommend withholding biologic therapies before hip and knee arthroplasty, yet evidence to inform optimal timing is limited. The aim of this study was to determine whether withholding abatacept infusions is associated with lower risk of adverse postoperative outcomes. Methods: This retrospective cohort study, which used US Medicare and Truven MarketScan administrative data from January 2006 to September 2015, evaluated adults with rheumatoid arthritis who received intravenous abatacept (precisely dated in claims data) within 6 months of elective primary or revision hip or knee arthroplasty. Propensity weighted analyses using inverse probability weights compared the risk of 30-day hospitalized infection and 1-year prosthetic joint infection (PJI) between patients with different abatacept stop timing (time between last infusion and surgery). Secondary analyses evaluated nonurinary hospitalized infections and 30-day readmissions. Results: After 1,939 surgeries among 1,780 patients, there were 175 hospitalized infections (9.0%), 115 nonurinary hospitalized infections (5.9%), 39 PJIs (2.4/100 person-years), and 114/1,815 30-day readmissions (6.3%). There were no significant differences in outcomes with abatacept stop timing <4 weeks (1 dosing interval) versus 4–8 weeks (hospitalized infection odds ratio [OR] 0.93 [95% confidence interval (95% CI) 0.65–1.34]; nonurinary hospitalized infection OR 0.93 [95% CI 0.60–1.44]; PJI hazard ratio 1.29 [95% CI 0.62–2.69]; 30-day readmission OR 1.00 [95% CI 0.65–1.54]). Similarly, there were no significant differences in outcomes with abatacept stop timing <4 weeks versus ≥8 weeks. Glucocorticoid use >7.5 mg/day was associated with greater risk of hospitalized infection (OR 2.19 [95% CI 1.28–3.77]) and nonurinary hospitalized infection (OR 2.38 [95% CI 1.22–4.64]). Conclusion: Compared to continuing intravenous abatacept, withholding abatacept for ≥4 weeks (one dosing interval) before surgery was not associated with a lower risk of hospitalized infection, nonurinary hospitalized infection, PJI, or 30-day readmission.