Objective: Research has demonstrated that a lack of social support is related to suicide risk. This study examines perceived burdensomeness and thwarted belongingness, of the Interpersonal Theory of Suicide, as mechanisms of the social support–suicide relationship in college students. Method: The study consisted of 207 students from a Midwestern university. Data were collected from 2007 to 2008. Two multiple mediation analyses were conducted to examine whether perceived burdensomeness and thwarted belongingness mediated the relationship between indices of social support and suicide ideation. Results: Perceived burdensomeness mediated the relationships between perceived social support and suicide ideation (95% confidence interval [CI] −.02 to −.00, effect size = −.01) and social connectedness and suicide ideation (95% CI −.03 to −.00, effect size = −.03). Thwarted belongingness did not mediate either relationship. Conclusions: Results suggest that a lack of social support could lead to perceptions of being a burden on others, which could lead to suicide ideation.