Obstructive sleep apnea (OSA) is seen in approximately 60% to 70% of patients with stroke or ischemic heart disease (IHD). The relationship between OSA and recurrent vascular events and all-cause mortality remains inconclusive. We aimed to systematically evaluate the associations between OSA and serious adverse outcomes following stroke or IHD by a meta-analysis of prospective cohort studies. We searched MEDLINE and EMBASE in August 2014 for studies that evaluated the prospective associations between OSA and the risk of stroke, IHD, and death among stroke or IHD patients. Outcome data were pooled using random effects meta-analysis. Subgroup, heterogeneity, and sensitivity analyses and publication bias were performed. Of 13 hospital-based cohort studies included, 5 reported results on stroke (n = 860), 6 reported on IHD (n = 1083), and 11 reported on all-cause death or cardiovascular death (n = 1930). OSA was significantly associated with the risk of stroke, IHD, and all-cause mortality after stroke or IHD. The pooled relative risks were 1.94 (95% confidence interval [CI], 1.29-2.92) for stroke, 1.83 (95% CI, 1.15-2.93) for IHD, and 1.59 (95% CI, 1.33-1.89) for all-cause mortality. There was no evidence of significant between-study heterogeneity. The results did not materially change in the sensitivity analyses for the outcomes of stroke and all-cause mortality. OSA may be a significant predictor of serious adverse outcomes following stroke or IHD. More high-quality studies are needed to determine if better treatment of OSA leads to fewer recurrent vascular events, especially a large-scale, multicenter randomized-controlled trial.