Physical activity (PA) and exercise programmes are recommended for the management of fibromyalgia. Despite positive effects on symptoms and function, PA promotion remains a significant clinical challenge. Behaviour change theories and techniques are recommended as part of complex health interventions; their integration into interventions aimed at PA behaviour in people with fibromyalgia is not known. This review explored behaviour change interventions targeting PA in adults with fibromyalgia. A systematic review was conducted; randomized and quasi-randomized controlled trials with at least one behaviour change intervention targeting PA were included. MEDLINE/OVID, EMBASE, PEDro, PsychINFO, CINAHL, Scopus, Web of Science, the Cochrane Central Register of Controlled Trials and relevant conference abstracts were searched. Two authors independently screened studies for inclusion and performed risk of bias assessments. Articles were reviewed for their use of behaviour change theory and behaviour change techniques (BCTs). The search identified 2491 records, from which eight studies (1416 participants) were included. PA and exercise behaviours were the primary focus of four interventions and were components of broader interventions in four studies. Behaviour change theories informed four interventions. Thirty-two different BCTs were used across studies. Five studies reported improvements in PA either post-intervention or at follow-up. Two studies used objective PA measures and seven studies used self-report measures. Short-term benefits in pain, quality of life, and physical fitness were also observed. Behaviour change interventions targeting PA in people with fibromyalgia have had limited success to date. With significant variations in intervention designs, the optimal intervention remains unknown