Objective Breast cancer has psychological consequences that impact quality of life. We examined factors associated with negative psychological consequences of a breast cancer diagnosis, in a diverse sample of 910 recently diagnosed patients (378 African American, 372 white, and 160 Latina). Methods Patients completed an in‐person interview as part of the Breast Cancer Care in Chicago study within an average of 4 months from diagnosis. The Cockburn negative psychological consequences of breast cancer screening scale was revised to focus on a breast cancer diagnosis. Path analysis assessed predictors of psychological consequences and potential mediators between race/ethnicity and psychological consequences. Results Compared to white counterparts, bivariate analysis showed African American (β = 1.4, P < .05) and Latina (β = 3.6, P < .001) women reported greater psychological consequences. Strongest predictors (P < .05 for all) included unmet social support (β = .38), and provider trust (β = .12), followed by stage at diagnosis (β = .10) and perceived neighborhood social disorder (β = .09).The strongest mediator between race/ethnicity and psychological consequences was unmet social support. Conclusions African American and Latina women reported greater psychological consequences related to their breast cancer diagnosis; this disparity was mediated by differences in unmet social support. Social support represents a promising point of intervention.