Obsessive–compulsive symptoms (OCS) in psychotic disorders are associated with unfavorable outcomes, whether this extends to cognitive function remains unclear. We conducted meta-analyses on several cognitive domains to investigate overall group differences between patients with a psychotic disorder and co-occurring OCS (OCS +) and those without OCS (OCS−). We used meta-regression to assess possible confounding effects. No overall associations between OCS + and OCS− in any of the 17 investigated cognitive domains were found. We predominantly found large heterogeneity in effect size and direction among studies. Post-hoc analyses of processing speed tasks not purely based on reaction-time showed worse performance in the OCS + group with a small effect size (SMD = − 0.190; p = 0.029). Meta-regression revealed advanced age was significantly correlated with worse performance of the OCS + group in processing speed (R2 = 0.7), working memory (R2 = 0.11), cognitive inhibition (R2 = 0.59), and cognitive flexibility (R2 = 0.34). Patients fulfilling the criteria for an obsessive–compulsive disorder showed less impairment in cognitive inhibition compared to the OCS + group (R2 = 0.63). Overall, comorbid OCS were not associated with cognitive impairment. However, large heterogeneity between studies highlights the complex nature of factors influencing cognition in people with psychotic disorder and comorbid OCS and warrants further research into possible moderating factors.