Background: The ongoing UNIFI long-term extension evaluates subcutaneous ustekinumab for moderate-to-severe ulcerative colitis (UC) from weeks 44 through 220. Aims: To assess efficacy (through week 92) and safety (through week 96) during the long-term extension. Methods: Overall, 399 responders to intravenous ustekinumab induction and who were randomised to maintenance therapy were treated in the long-term extension (115 received subcutaneous placebo, 141 received ustekinumab 90 mg every 12 weeks [q12w], and 143 received ustekinumab 90 mg q8w). Placebo treatment was discontinued at unblinding after week 44. Partial Mayo scores were collected every 12 weeks and at each dosing visit after unblinding. Safety was evaluated throughout. Results: Among all patients randomised in maintenance, symptomatic remission rates (stool frequency = 0/1; rectal bleeding = 0) at week 92 were, 64.5% and 67.6% in the ustekinumab q12w and q8w groups, respectively. Among randomised patients treated in the long-term extension, 78.7% and 83.2% of patients receiving q12w and q8w, respectively, attained symptomatic remission at week 92; >95% of patients in symptomatic remission at week 92 were corticosteroid-free. Both ustekinumab groups maintained efficacy through week 92. From weeks 44 to 96, adverse events (AEs) per hundred patient-years (PY) of follow-up for combined ustekinumab vs placebo were: 255.68 vs 267.93; serious AEs, 9.34 vs 12.69; malignancies (including non-melanoma skin cancers), 0.93 vs 1.49; and serious infections, 2.33 vs 2.99. One patient with multiple comorbidities who received one ustekinumab dose after dose adjusting from placebo experienced a fatal cardiac arrest. Conclusions: The efficacy of ustekinumab in patients with UC was sustained through 92 weeks. No new safety signals were observed (ClinicalTrials.gov number, NCT02407236).