Fibromyalgia syndrome (FMS) is a complex chronic condition, the treatment of which still poses many challenges. Complementary therapies (CT) have gained increasing popularity among FMS patients. Past reviews evaluating effectiveness of CT for treatment of FMS revealed some potential benefits arising from certain modalities. However, with the data available, it becomes difficult to formulate a unique opinion about this matter. In the present paper, the authors propose some guidelines to conciliate the expectations of patients with the lack of solid evidence, in a practicable yet responsible way. Many items should be considered before prescribing, proscribing, or tolerating a CT, besides results from randomized controlled trials, such as efficacy (mechanisms of action); effectiveness (effect in practice); efficiency (cost-benefit ratio); safety; risk-benefit ratio; legislation; healthcare service involvement; practitioner characteristics; objective (purpose); and the potential of combination with conventional treatment.