This review aimed to determine the effectiveness of positional modification techniques in preventing supine sleep, sleep-disordered breathing and other clinically important outcomes in patients with supine obstructive sleep apnea (OSA). Randomized controlled trials comparing positional modification techniques with any other therapy or placebo were included. Electronic searches of databases including CENTRAL, MEDLINE, CINAHL, Embase, and Web of Science up to April 2016 were performed. Meta-analysis was undertaken where possible. This comprehensive meta-analysis found benefit for positional modification techniques in those with supine OSA in terms of reduction in apnea-hypopnea index (AHI) and time spent supine. Whilst positional modification techniques were effective in terms of a reduction in AHI, continuous positive airway pressure (CPAP) was more effective than these techniques. A reliable diagnosis of supine OSA should be considered, and further research is required on patient-centred outcomes including comfort, barriers to adherence, cost-analysis, and long term outcomes including the effect on cardiovascular disease, the metabolic syndrome, and insulin resistance.