Obstructive sleep apnea (OSA), prevalent in patients with stroke, increases the risks of cardiovascular events and stroke. This meta-analysis evaluated the effectiveness of continuous positive airway pressure (CPAP) for preventing stroke in patients with OSA. Embase, PubMed, and Cochrane Central database (up to October 2019) were searched for studies that compared stroke risk in patients with OSA receiving CPAP or usual treatment. In total, 13 studies, comprising nine randomized control trials (RCTs) and four cohort studies, were included. The pooled odds ratio revealed significant stroke risk reduction in cohort studies but not in RCTs. In terms of the clinical heterogeneity observed, we further divided studies into subgroups based on CPAP adherence status and baseline OSA severity in the RCTs included. The subgroup analysis revealed significant stroke risk reduction in good CPAP adherence group and moderate to severe OSA group. In conclusion, the meta-analysis suggests that CPAP therapy may reduce the risk of stroke in patients with good adherence and patients with moderate to severe OSA. Further researches should focus on improving CPAP adherence in patients with stroke and assessing the effectiveness of other treatments (e.g., oral appliances or positional therapy) for preventing stroke.