Currently, anti-TNFα antibodies are used to treat Crohn's disease. We report on a 45-year-old Japanese female with Crohn's disease developing SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome following exposure to the anti-TNFα antibody adalimumab. Initially, adalimumab induced remission, but the patient showed SAPHO syndrome 11 weeks following the start of adalimumab therapy for the first time. Cutaneous and articular involvement were exacerbating the condition, so adalimumab was discontinued and the patient was put on low-dose methotrexate to control her symptoms. To our knowledge, this is the first report of SAPHO syndrome occurring during anti-TNF therapy, which is thought to be a paradoxical response to adalimumab.