© 2017 American Academy of Dermatology, Inc. Background Previous clinical trials have not evaluated improvement in nail psoriasis as a primary end point. Objective This phase 3 trial evaluated the safety and efficacy of adalimumab in patients with moderate-to-severe fingernail psoriasis and moderate-to-severe plaque psoriasis. Methods Patients were randomized 1:1 to 40 mg adalimumab every other week or placebo. The primary efficacy end point was at least 75% improvement in total-fingernail modified Nail Psoriasis Severity Index (NAPSI75) response rate at week 26. Ranked secondary end point scores evaluated at week 26 were total-fingernail NAPSI and modified NAPSI, nail pain, Nail Psoriasis Physical Functioning Severity, Brigham Scalp Nail Inverse Palmo-Plantar Psoriasis Index, and Physician's Global Assessment (fingernail psoriasis). Results Of the 217 randomized patients (108 received placebo and 109 received adalimumab), 188 (86.6%) completed 26 weeks of treatment (period A) or escaped early to the open-label period. The study met the primary end point (response rate of 3.4% with placebo vs 46.6% with adalimumab [P <.001]) and all ranked secondary end points. The serious adverse event rates (placebo vs adalimumab) in period A were 4.6% versus 7.3%; the serious infections rates were 1.9% versus 3.7%. Limitations Patients with less than 5% BSA involvement were not eligible for enrollment. Conclusions After 26 weeks of adalimumab treatment, significant improvements were seen in the primary and all ranked secondary end points and in signs and symptoms of moderate-to-severe nail psoriasis versus with placebo and no new safety risks were identified.