Purpose This meta-analysis examined relationships between social support and self-care in type 1 (T1DM) and 2 diabetes mellitus (T2DM). Methods We searched for published and unpublished studies using the following databases: PubMed, Embase, PsycINFO, the Cochrane Library, and Medline. MeSH search terms included "diabetes mellitus," "social support," "caregiver," "self-care," "self-management," "self-care skills," and "coping behavior." Studies reporting correlations between social support and self-care were included. Results Initially, 2 095 studies were extracted. After eliminating duplicate and irrelevant studies, 28 studies involving 5 242 patients with diabetes were included. Of these, 22 studies examined T2DM subjects. Social support was significantly associated with self-care ( k = 28, r = .28, 95% CI: .21-.34, P < .001). Among the diabetes self-care types, the strongest effect was found for glucose monitoring ( k = 6, r = .21, 95% CI: .08-.33). The relationship between social support and self-care was stronger in T2DM ( k = 22, r = .30, 95% CI: .22-.37), relative to T1DM, samples ( k = 5, r = .22, 95% CI: .02-.38). Conclusion It was concluded that the overall effect size for social support on self-care was moderate, and its strength differed by ethnic majority within the sample, type of social support measures, and publication status.