Objective: Three biological agents (adalimumab, etanercept and infliximab) are registered for psoriatic arthritis (PsA) by the EMEA or the FDA. Our objectives were to compare the efficacy of the available biologicals in PsA and to compare their effect sizes by standardized improvement criteria of signs and symptoms. Methods: Randomized controlled trials (RCT) of adalimumab, etanercept and infliximab involving patients with PsA were searched in MEDLINE by Cochrane Highly Sensitive Search Strategy. The quality of selected studies was measured using the Jadad-score. Two clinical outcomes were analyzed: the rate of patients achieving at least 20% improvement by the American College of Rheumatology criteria (ACR20) and the Psoriatic Arthritis Response Criteria (PsARC). Review Manager 4.2 software was applied for the analysis, using the number needed to treat (NNT) and relative risk (RR) as statistical variables. Due to lack of face-to-face evidence on biologicals, indirect comparison was conducted applying Butcher's method. Results: Six RCTs were identified involving altogether 982 patients on the active treatment arms: adalimumab (n= 413), etanercept (n=265) and infliximab (n=304). All trials were placebo controlled, the primary follow-up time was 12-16 weeks and the primary outcome was ACR20. The NNTs (95% confidence intervals) for adalimumab, etanercept and infliximab were 2.6 (2.1-3.2), 2.1 (1.7-2.7) and 2.0 (1.7-2.4) patients to achieve ACR20 outcome and 2.9 (2.3-4.0), 2.2 (1.8-2.8) and 2.0 (1.6-2.4) to fulfill PsARC outcome, respectively. Indirect pairwise comparisons of TNF-alpha inhibitors yielded the RR of 0.87 (0.50-1.51) for adalimumab vs. etanercept, of 1.37 (0.72-2.61) for infliximab vs. etanercept and of 1.57 (0.87-2.86) for infliximab vs. adalimumab. Conclusion: Adalimumab, etanercept and infliximab are effective for the treatment of PsA. Both the NNTs and the responsiveness of the three drugs at PsARC and ACR20 outcomes are similar. Indirect comparison did not reveal significant difference in the efficacy among the TNF-alpha inhibitors in PsA.