BACKGROUND: Long-term safety evaluations of biologics are needed to inform patient management decisions. OBJECTIVES: To evaluate the safety of ustekinumab in patients with moderate-to-severe psoriasis treated for up to 5 years. METHODS: Safety data were pooled from four studies of ustekinumab for psoriasis. Rates of adverse events (AEs), serious AEs (SAEs) and AEs of interest [infections, nonmelanoma skin cancers (NMSCs), other malignancies and major adverse cardiovascular events (MACE)] per 100 patient-years (PY) of follow-up were analysed by ustekinumab dose (45 or 90 mg) and by year of follow-up (years 1-5) to evaluate the dose response and impact of cumulative exposure. Observed rates of overall mortality and other malignancies were compared with those expected in the general U.S. population. RESULTS: Analyses included 3117 patients (8998 PY) who received one or more doses of ustekinumab, with 1482 patients treated for ≥4 years (including 838 patients ≥5 years). At year 5, event rates (45 mg, 90 mg, respectively) for overall AEs (242·6, 225·3), SAEs (7·0, 7·2), serious infections (0·98, 1·19), NMSCs (0·64, 0·44), other malignancies (0·59, 0·61) and MACE (0·56, 0·36) were comparable between dose groups. Year-to-year variability was observed, but no increasing trend was evident. Rates of overall mortality and other malignancies were comparable with those expected in the general U.S. population. CONCLUSIONS: No dose-related or cumulative toxicity was observed with increasing duration of ustekinumab exposure for up to 5 years. Rates of AEs reported in ustekinumab psoriasis trials are generally comparable with those reported for other biologics approved for the treatment of moderate-to-severe psoriasis.