BackgroundIntact cognitive function is crucial for healthy aging. Functional social support is thought to protect against cognitive decline. We conducted a systematic review to investigate the association between functional social support and cognitive function in middle- and older-aged adults.MethodsArticles were obtained from PubMed, PsycINFO, Sociological Abstracts, CINAHL, and Scopus. Eligible articles considered any form of functional social support and cognitive outcome. We narratively synthesized extracted data by following the Synthesis Without Meta-Analysis (SWiM) guidelines and assessed risk of bias using the Newcastle–Ottawa Scale (NOS).ResultsEighty-five articles with mostly low risk-of-bias were included in the review. In general, functional social support—particularly overall and emotional support—was associated with higher cognitive function in middle- and older-aged adults. However, these associations were not all statistically significant. Substantial heterogeneity existed in the types of exposures and outcomes evaluated in the articles, as well as in the specific tools used to measure exposures and outcomes.ConclusionsOur review highlights the role of functional social support in the preservation of healthy cognition in aging populations. This finding underscores the importance of maintaining substantive social connections in middle and later life.Systematic review registrationRutter EC, Tyas SL, Maxwell CJ, Law J, O'Connell ME, Konnert CA, Oremus M. Association between functional social support and cognitive function in middle-aged and older adults: a protocol for a systematic review. BMJ Open;10(4):e037301.https://doi.org/10.1136/bmjopen-2020-037301Supplementary InformationThe online version contains supplementary material available at 10.1186/s13643-023-02251-z.