Guselkumab, an interleukin-23 blocker, was superior to adalimumab in treating moderate to severe psoriasis in a phase II trial. We sought to compare efficacy and safety of guselkumab with adalimumab and placebo in patients with psoriasis treated for 1year. Patients were randomized to guselkumab 100mg (weeks 0 and 4, then every 8weeks; n=329); placebo→guselkumab (weeks 0, 4, and 12 then guselkumab at weeks 16 and 20, then every 8weeks; n=174); or adalimumab (80mg week 0, 40mgweek 1, then 40mg every 2weeks through week 47; n=334). Physician-reported outcomes (Investigator Global Assessment, Psoriasis Area and Severity Index [PASI]), patient-reported outcomes (Dermatology Life Quality Index, Psoriasis Symptoms and Signs Diary), and safety were evaluated through week 48. Guselkumab was superior (P<.001) to placebo at week 16 (85.1% vs 6.9% [Investigator Global Assessment score of 0/1 (cleared/minimal)] and 73.3% vs 2.9% [90% or greater improvement in PASI score from baseline (PASI 90)]). Guselkumab was also superior (P<.001) to adalimumab for Investigator Global Assessment 0/1 and PASI 90 at week 16 (85.1% vs 65.9% and 73.3% vs 49.7%), week 24 (84.2% vs 61.7% and 80.2% vs 53.0%), and week 48 (80.5% vs 55.4% and 76.3% vs 47.9%). Furthermore, guselkumab significantly improved patient-reported outcomes through week 48. Adverse event rates were comparable between treatments. Analyses were limited to 48weeks. Guselkumab demonstrated superior efficacy compared with adalimumab and was well tolerated in patients with psoriasis through 1year.