Objectives To evaluate real-world persistence and effectiveness of the IL-12/23 inhibitor, ustekinumab or a tumour necrosis factor inhibitor (TNFi) for psoriatic arthritis over 3 years. Methods PsABio ( NCT02627768 ), a prospective, observational study, followed patients with PsA prescribed first-line to third-line ustekinumab or a TNFi. Persistence and effectiveness (achievement of clinical Disease Activity for PSA (cDAPSA) low disease activity (LDA)/remission and minimal disease activity/very LDA (MDA/VLDA)) were assessed every 6 months. Safety data were collected over 3 years. Analyses to compare the modes of action were adjusted on baseline differences by propensity scores (PS). Results In 895 patients (mean age 49.8 years, 44.7% males), at 3 years, the proportion of patients still on their initial treatments was similar with ustekinumab (49.9%) and TNFi (47.8%). No difference was seen in the risk of stopping/switching; PS-adjusted hazard ratio (95% CI) for stopping/switching ustekinumab versus TNFi was 0.87 (0.68 to 1.11). In the overall population, cDAPSA LDA/remission was achieved in 58.6%/31.4% ustekinumab-treated and 69.8%/45.0% TNFi-treated patients; PS-adjusted ORs (95% CI) were 0.89 (0.63 to 1.26) for cDAPSA LDA; 0.72 (0.50 to 1.05) for remission. MDA/VLDA was achieved in 41.4%/19.2% of ustekinumab-treated and 54.2%/26.9% of TNFi-treated patients with overlapping PS-adjusted ORs. A greater percentage of TNFi-treated patients achieved effectiveness outcomes. Both treatments exhibited good long-term safety profiles, although ustekinumab-treated patients had a lower rate of adverse events (AEs) versus TNFi. Conclusion At 3 years, there was generally comparable persistence after ustekinumab or TNFi treatment, but AE rates were lower with ustekinumab.