We evaluated the efficacy, pharmacokinetics, and safety of adalimumab in Japanese patients with active ankylosing spondylitis (AS) who had an inadequate response to, or who were intolerant of, treatment with ≥1 nonsteroidal anti-inflammatory drugs (NSAIDs). This phase 3, multicenter, open-label trial assessed the percentage of patients with a 20% response in the Assessment of SpondyloArthritis international society working group criteria (ASAS20) at week 12 as the primary endpoint. Secondary outcome measures included assessments of disease activity, clinical response, functionality, and spinal mobility at weeks 12 and 60. Serum trough adalimumab concentrations were summarized using descriptive statistics. The adverse event profile was summarized for patients who received at least one dose of the study drug during the assessment period. At week 12, 73.2% (30/41) achieved an ASAS20 response and nearly 40% met ASAS partial remission criteria; proportions were maintained after up to 60 weeks of therapy. Mean adalimumab concentrations reached steady-state between weeks 12 and 20. Adalimumab was generally safe and well tolerated, with approximately 90% of adverse events considered to be mild. These results support the use of adalimumab as a safe and effective therapy for Japanese patients with active AS.