This study assessed the extent to which associations between perceived and received social support from family and friends and changes in older adults’ cognitive function were moderated by educational attainment. Sibling pairs in the Wisconsin Longitudinal Study (WLS) (N = 4,297) completed a survey about social support in 2011 and a cognitive battery in 2011 and 2020. Participants’ mean age in 2020 was 80.2 years old. Multilevel linear regressions indicated that perceived, but not received, support from friends was associated with better cognitive function 9 years later. Perceived family support was cognitively advantageous for older adults at most levels of educational attainment. However, among postgraduates, perceived family support was unrelated to cognitive function. That the association between perceived support and cognitive function differs based on educational attainment gives interventionists additional information needed to identify groups of older adults most susceptible to cognitive impairment.