Objective To evaluate the safety and efficacy of intravenous ( IV ) golimumab treatment in psoriatic arthritis (PsA). Methods In this phase III , randomized, double‐blind, placebo‐controlled trial, patients were randomly assigned to receive IV placebo (n = 239) or golimumab at 2 mg/kg (n = 241) at weeks 0, 4, 12, and 20. The primary end point was the proportion of patients meeting the American College of Rheumatology 20% improvement criteria (achieving an ACR 20 response) at week 14. Controlled secondary end points included change from baseline in Health Assessment Questionnaire disability index ( HAQ DI ) score at week 14, proportions of patients with ACR 50 and ACR 70 responses and ≥75% improvement on the Psoriasis Area and Severity Index (a PASI 75 response) at week 14, and change from baseline at week 24 in the total modified Sharp/van der Heijde score ( SHS ) with modifications for patients with PsA. Results At week 14, an ACR 20 response was achieved by 75.1% of patients in the golimumab group compared with 21.8% of patients in the placebo group ( P < 0.001). Greater proportions of golimumab‐treated patients had an ACR 50 response (43.6% versus 6.3%), an ACR 70 response (24.5% versus 2.1%), and a PASI 75 response (59.2% versus 13.6%) at week 14 ( P < 0.001 for all). Patients in the golimumab group had greater mean changes at week 14 in HAQ DI score (–0.60 versus –0.12; P < 0.001). At week 24, the mean change in total PsA‐modified SHS was –0.4 in the golimumab group and 2.0 in the placebo group ( P < 0.001). Through week 24, 40.6% of patients in the placebo group and 46.3% of patients in the golimumab group had ≥1 adverse event ( AE ); infections were the most common type. Conclusion Patients receiving IV golimumab at 2 mg/kg had significantly greater improvements in the signs and symptoms of PsA and less radiographic progression through week 24. AE s were consistent with those seen with other anti–tumor necrosis factor agents.