Fibromyalgia (FM) is a common and often debilitating chronic pain condition. Research shows that symptoms of depression and anxiety are present in up to three quarters of individuals with FM. Of concern, most adults with FM cannot access traditional face-to-face cognitive behavioural pain management programs, which are known to be beneficial. Given known difficulties with treatment access, the present study sought to explore the efficacy and acceptability of a previously developed Internet-delivered cognitive behavioural pain management course, the Pain Course, for adults with FM. The five-lesson course was delivered over eight weeks and was provided with brief weekly contact, via telephone and secure email, with a guide throughout the course. Participants were randomized either to the Pain Course (n = 30) or to a waiting-list control group (n = 30). Symptoms were assessed at pre-treatment, post-treatment and 4-week follow-up. Completion rates (87%) and satisfaction ratings (86%) were high. Improvements were significantly greater in treatment group participants compared to waiting-list group participants on measures of FM (Cohen's d =.70; 18% reduction), depression (Cohen's d =.63-.72; 20-28% reduction), pain (Cohen's d =.87; 11% improvement) and fear of pain (Cohen's d =1.61; 12% improvement). Smaller effects were also observed on measures of generalized anxiety and physical health. The changes were maintained at four-week follow-up. The current findings add to existing literature and highlight the specific potential of Internet-delivered cognitive behavioural pain management programs for adults with FM, especially as a part of stepped-care models of care. Future research directions are described.