Understanding what motivates suicidal behavior is critical to effective prevention and clinical intervention. The Inventory of Motivations for Suicide Attempts (IMSA) is a self-report measure developed to assess a wide variety of potential motivations for suicide. The purpose of this study is to examine the measure’s psychometric and descriptive properties in two distinct populations: 1) adult psychiatric inpatients (n = 59) with recent suicide attempts (median of 3 days prior) and 2) community participants assessed online (n = 222) who had attempted suicide a median of 5 years earlier. Findings were very similar across both samples and consistent with initial research on the IMSA in outpatients and undergraduates who had attempted suicide. First, the individual IMSA scales demonstrated good internal reliability and were well represented by a two factor superordinate structure: 1) Internal Motivations and 2) Communication Motivations. Second, in both samples unbearable mental pain and hopelessness were the most common and strongly endorsed motivations, while interpersonal influence was the least endorsed. Finally, motivations were similar in men and women — a pattern that previous work was not in a position to examine. Taken together with previous work, findings suggest that the nature, structure, and clinical correlates of suicide attempt motivations remain consistent across diverse individuals and situations. The IMSA may serve as a useful tool in both research and clinical contexts to quickly assess individual suicide attempt motivations.