The Interpersonal Theory of Suicide (IPTS) has received support for its role in understanding suicidal thoughts and behaviors. However, few longitudinal studies have focused on testing this theory in university students. The present study aimed to confirm the theoretical model of the IPTS in a sample of 225 Spanish university students, using path analysis in a longitudinal study. We assessed thwarted belongingness and perceived burdensomeness at T1 and hopelessness and suicidal ideation at T2, 12-14 weeks later. Moreover, we assessed suicidal ideation weekly for 14 weeks. Path analyses confirmed the Interpersonal Theory of Suicide model, with thwarted belongingness and perceived burdensomeness as direct and indirect predictors of suicidal ideation through hopelessness. Providers of guidance and clinical services in university settings should be trained to identify perceived burdensomeness, social belongingness, hopelessness, and suicidal ideation when screening for suicide prevention.