The goal of the present study is to examine the construct validity of a self-report questionnaire—the Interpersonal Needs Questionnaire—designed for use in research on the etiology of suicidal behavior, as well as in clinical settings as a component of risk assessments. The overarching aim of the current project was to develop a viable latent variable measurement model of the INQ: results from two EFA's in a CFA framework and a single-group CFA using three undergraduate samples support the viability of a latent variable measurement model of the INQ with 14 indicators of the construct of thwarted belongingness and eight indicators of the construct of perceived burdensomeness. These data are consistent with the assumption of the Interpersonal Theory of Suicide that thwarted belongingness and perceived burdensomeness are related, but distinct constructs. Results also indicated that the measurement model developed using undergraduates is a viable model for both clinical outpatients and elder adults. Finally, strong evidence for convergent and discriminant validity was found for the thwarted belongingness latent variable, while results were equivocal for perceived burdensomeness latent variable. Data from the current project suggest that the INQ measures two constructs especially relevant for suicide prevention and thus may be a useful addition to risk assessment protocols.