BACKGROUND & AIMS: There is limited evidence on real-world patterns and safety of biologic switch timing in patients with ulcerative colitis (UC)/Crohn's disease (CD). This study investigated biologic therapy switch occurrence in real-world practice and compared the risk of any infection and serious infection between patients with overlapping (OS) vs non-overlapping switches (NOS). METHODS: This retrospective observational study identified patients with UC/CD initiating biologic therapy between September 1, 2017, and August 31, 2022, in Optum's de-identified Clinformatics Data Mart Database. Crude incidence rates (IRs) per 1000 person-years (PYs) and timing of switch were assessed. Biologic switch events were categorized as OS (switch to another biologic within </=5 half-lives after discontinuation of initial biologic) or NOS (switch to another biologic >5 half-lives after discontinuation of initial biologic). Inverse probability of treatment weighted Cox proportional hazards modeling estimated adjusted hazard ratios (aHRs) of any infection and serious infection associated with switch timing. RESULTS: Among 11,992 adult patients newly initiating a biologic therapy for UC/CD, 1293 patients underwent a biologic switch, 64.2% of which were considered an OS. Adjusted IRs per 1000 PYs, for any infection, were comparable across switching groups. No significant differences in the aHRs of infections were found between OS and NOS (any infection: aHR, 1.40; P = .17; serious infection: aHR, 0.95; P = .93). CONCLUSION: OSs were common and not associated with an increased risk of serious infection vs non-overlapping biologics. Shortened washout periods may pose minimal safety risks to patients while improving UC/CD therapy management and improving trial recruitment.