Cognitive behavioural therapy (CBT) is an effective psychological treatment for anxiety-related disorders (anxiety disorders, post-traumatic stress disorder, and obsessive-compulsive disorder). However, relapse of anxiety symptoms is common following completion of treatment. This study aimed to identify predictors of relapse of anxiety after CBT for adult (18+) patients to enable the identification of "at-risk" patients who could potentially benefit from relapse prevention interventions. A systematic review and meta-analysis were conducted, including studies found in PsycINFO, PubMed, Scopus, and Web of Science, and through hand-searches of references lists and reverse citations. Nine studies met eligibility criteria (N = 532 patients). On average, 23.8% of patients experienced relapse following completion of CBT. A total of 21 predictors were identified and grouped into seven categories: residual symptoms; personality disorders; medication; clinical features; stressful life-events; degree of improvement; and demographics. A meta-analysis of residual symptoms as a predictor of relapse yielded a moderate but non-significant-pooled effect size (r = 0.35; 95% CI −0.21, 0.74, p =.08). Further research with adequately powered samples and standardised operationalisations of relapse are required to identify robust predictors. [ABSTRACT FROM AUTHOR]