Cognitive models of post-traumatic stress disorder (PTSD) suggest maladaptive appraisals play a central role in the aetiology of this disorder. The current meta-analysis sought to provide a comprehensive, quantitative examination of the relationship between maladaptive appraisals and PTSD. One-hundred and 35 studies met study inclusion criteria and were subject to random effects meta-analysis. A large effect size was found for the relationship between appraisals and PTSD (r = 0.53, 95% CI = 0.51-0.56, k = 147), albeit with significant heterogeneity. In studies using only the Posttraumatic Cognitions Inventory or Child Post-traumatic Cognitions Inventory, the effect size remained large (r = 0.56; k = 104). In adults, appraisals about the self had a large effect size (r = 0.61), appraisals about the world had a medium effect size (r = 0.46) and self-blame appraisals had a small effect size (r = 0.28). In child/adolescent studies, large effect sizes were found for both 'fragile person in a scary world' and 'permanent and disturbing change' appraisals (r = 0.54 and r = 0.60, respectively). The effect size remained large in prospective longitudinal studies up to one year after trauma. There was no moderation effect for civilian vs military populations, questionnaire vs interview measures of PTSD, single vs multiple trauma exposure, or intentional vs unintentional trauma. The main effect size estimate was robust to sensitivity analyses concerning statistics used, study quality and outliers. These findings are consistent with the strong role for maladaptive appraisals in the aetiology of PTSD proposed by cognitive models. In particular, the role of self-appraisals in adults was highlighted. Avenues for future research include more studies in child, multiple trauma and military populations and longer-term follow up studies.