The prevalence of Alzheimer’s disease and cognitive decline is especially elevated among Black Americans. Emerging work has shown that perceived discrimination is implicated in accelerated brain aging, cognitive decline, and worse global cognition, but the mechanisms underlying these associations remain unclear. As a form of social rejection, discrimination may lead to alienation, reduced sense of belonging, and social withdrawal. Therefore, loneliness and social isolation may be downstream consequences of discrimination that also contribute to lower cognition. Research suggests that people who are socially isolated and/or lonely appear to show heightened vigilance to social cues during interactions, which may increase perceived discrimination in the future, as well. This study examined the reciprocal processes among loneliness, social isolation, and discrimination and their associations with changes in cognition. The study included 1,281 Black adults ages 50+ from pooled half-samples in the 2010 to 2020 waves of the Health and Retirement Study. Random intercept cross-lagged panel models (RI-CLPM) estimated bidirectional relationships over time. Results indicated that perceived discrimination was significantly associated with increased social isolation over time. Social isolation was also a significant predictor of greater perceived discrimination and worse cognition over time. However, loneliness was not associated with discrimination or cognition in these models. Findings indicated that social isolation, but not loneliness, was a precursor and outcome of discrimination, and that social isolation may be a critical mechanism linking discrimination to worse cognitive outcomes. Future research is needed to examine protective factors that may moderate (e.g., social support, purpose in life) this association.