Oscillating positive expiratory pressure (OPEP) devices are intended to facilitate sputum clearance in chronic obstructive pulmonary disease (COPD), but there is uncertainty as to their place in treatment pathways. We aimed to review the existing literature to establish the evidence base for their use.A systematic search of records up to March 2020 was performed on PubMed, CINAHL, Medline (Ovid), Cochrane and Embase to retrieve clinical trials that evaluated the efficacy of OPEP devices in patients with COPD. Two independent reviewers retrieved the titles, abstracts and full texts, and completed the data extraction.Following full-text review of 77 articles, eight (six randomised control trials and 2 cross-over studies) were eligible for inclusion. Pooled analysis showed low-grade evidence that the use of OPEP devices was associated with decreased COPD symptoms and exacerbations (OR 0.37, 95% CI 0.19 to 0.72), and enhanced exercise capacity; 6 min walk distance (mean difference (95% CI), 49.8 m (14.2 m to 85.5 m); p=0.009]). However, studies were mostly short term with the majority having a high risk of bias. The average acceptance, completion and drop-out rates were 82%, 91% and 8%, respectively.The use of OPEP devices can have a positive impact in COPD, but confidence in effect sizes is low and there is a need for further, higher quality studies to examine their long-term efficacy in COPD as well as to identify specific patient phenotypes that are more likely to respond.CRD 42016041835.