Objective: The interpersonal-psychological theory of suicide hypothesizes proximal causes of suicidal ideation and behaviors; however, past studies have generally tested distal relations. The present study tested the proximal nature of the theory’s hypotheses. Methods: A repeated-measures design collected daily survey data on the theory constructs over 90 days from 206 (150 women) college students with previous histories of suicidal ideation. Participants completed 7,342 (39.6%) of the 18,540 surveys sent. Results: Thwarted belongingness and perceived burdensomeness both positively associated with passive suicidal ideation at the daily level. A statistical trend revealed that perceived burdensomeness was associated with daily active suicidal ideation only at high levels of thwarted belongingness and hopelessness. Active suicidal ideation, but not capability for suicide, was positively associated with suicidal behavior at the daily level. Conclusions: These results support the theory’s predictions regarding passive and active suicidal ideation, with limited support regarding suicidal behaviors. The proximal associations of the IPTS constructs with daily suicidal ideation suggest areas for potential intervention with suicidal clients.