Fibromyalgia (FM) is a condition that affects approximately 1,050,000 Canadians. Symptoms of depression and/or anxiety are present in up to three quarters of individuals with FM. A large percentage of individuals with FM, however, fail to seek psychological treatment for these symptoms, suggesting the need for the development of more accessible treatment methods, such as Internet-delivered cognitive behaviour therapy (ICBT). There has been limited research on the use of ICBT for FM and no research within the Canadian context. The focus of the current study was to assess the efficacy of the Pain Course, an ICBT program originally developed for pain patients, adapted for use for FM, referred to as the Pain Course for Fibromyalgia course. In this study, we were interested in the impact of the FM Course on FM symptoms, pain, depression and/or anxiety, and improving overall quality of life post-treatment. The course was administered to a randomized group of 30 individuals with FM and compared to a group of 30 individuals with FM who received standard care alone. Further objectives of the current study were to examine patient satisfaction, and determine whether the level of anxiety and depression mediated the impact of ICBT on FM symptom severity. The results of the current study provided evidence for the efficacy of an ICBT course in treating FM symptoms, anxiety, and depression among individuals diagnosed with FM. The current study identified small to moderate (i.e., .21-.56) between-group effect sizes across FM, anxiety, and depression symptoms. Furthermore, individuals with FM were highly satisfied with the ICBT program. Finally, mediation analyses revealed that FM severity was not significantly associated with either anxiety or depressive symptoms. Consequently, anxiety and depression symptoms were not found to mediate the association between ICBT and the severity of FM. In the future, researchers should provide ICBT for FM within primary healthcare and rehabilitation settings in conjunction with other forms of care. Results from the current study can support health professionals in establishing future areas in which to direct their research and enable improvement to the clinical management and the health status of individuals with FM using ICBT.