Disrupted social connectedness is associated with suicidal thoughts and behaviors among individuals with substance use disorders (SUDs). The current study sought to further characterize this relationship by examining several indices of social connectedness--(a) living alone, (b) perceived social support, (c) interpersonal conflict, and (d) belongingness. Participants (n = 814) were recruited from 4 residential substance-use treatment programs and completed self-report measures of social connectedness as well as whether they had ever thought about or attempted suicide. Multivariate results indicated that interpersonal conflict and belongingness were significant predictors of a history of suicidal ideation, and that belongingness, perceived social support, and living alone were significant predictors of suicide attempt. These results indicate the most consistent support for the relationship between suicidality and thwarted belongingness, and also support the clinical utility of assessing whether individuals live alone.