Background: Obstructive sleep apnoea (OSA) is highly prevalent and significantly associated with major adverse cardiovascular events (MACEs). Continuous positive airway pressure (CPAP) treatment has a protective effect on cardiovascular events in OSA patients. However, whether CPAP therapy significant reduces the risk of recurrent cardiovascular (CV) events in OSA patients with established cardiovascular or cerebrovascular diseases remains disputed. We aim to evaluate the effect of CPAP on recurrent cardiovascular outcomes in moderate to severe OSA patients with previous cardiovascular or cerebrovascular diseases. Methods: We searched the electronic databases (PubMed, EMBASE, and Cochrane library) from their inception to August, 2021. Only randomized controlled trials (RCTs) that described the association of CPAP treatment in patients with cardiovascular or cerebrovascular disease and OSA were included in our analysis. The primary outcome of interest was major adverse cardiac or cerebral events (MACCEs), a composite endpoint of myocardial infraction (MI), non-fatal stroke, CV mortality; secondary outcomes included all-caused death, cardiac mortality, myocardial infraction, atrial fibrillation, heart failure, repeat revascularization, angina, stroke, and transient ischemic attack. In addition, subgroup analyses based on CPAP adherence were performed. Result: Six RCTs of 4493 participants were included in the analysis. Compared with usual care, CPAP therapy did not significantly reduce the risk of recurrent MACCEs odds ratio (OR) 0.94, 95% confidence interval (CI) 0.79–1.12, p = 0.5, CV mortality (OR 0.83, 95% CI [0.54–1.26], p = 0.37), myocardial infarction (OR 1.09, 95% CI [0.8–1.47], p = 0.6), heart failure (OR 0.94, 95% CI [0.66–1.33], p = 0.71), stroke (OR 0.9, 95% CI [0.67–1.23], p = 0.52), or all-cause death (OR 0.86, 95% CI [0.63–1.16], p = 0.32). However, the subgroup analyses revealed that CPAP can decrease the risk of CV mortality (OR 0.25, 95% CI [0.08–0.77], p = 0.02) and stoke (OR 0.39, 95% CI [0.15–0.97], p = 0.04) in patients who used it more than 4 hours. Conclusions: CPAP therapy was not associated with reduce the risk of MACCEs in OSA patients with a history of chronic cardiovascular disease who utilize CPAP 4 hours/night, although CPAP appeared to have a positive effect on CV mortality and stroke among those who used CPAP >4 hours. The correlation between CPAP and the prognosis of OSA patients warrants further study.