Social support has well-documented mental-health benefits. However, research on instrumental support, a domain of social support, has yielded inconsistent results, which may be attributable to shortcomings in extant instrumental-support measures, including insufficient content coverage and confounding with personality and cognitive variables. The present research aims to develop and validate the Instrumental Support Inventory for Spouses (ISI-s), a self-report measure of enacted instrumental support received from a romantic partner. In Study 1, a sample of 372 married Amazon Mechanical Turk workers was recruited. Exploratory factor analysis was conducted on a large pool of items to guide factor retention and item selection, resulting in a 39-item inventory with five subscales: Logistic, Domestic, Childcare, Resource Provision, and Maintenance. Preliminary evidence of reliability and convergent validity was examined in this sample. Study 2 aimed to validate this inventory in a sample of 298 parents of children ages 0-12 and 69 of their romantic partners, using a 1-month retest longitudinal design. Further evidence was obtained for the reliability and factor structure of the ISI-s, and the inventory showed excellent convergent and discriminant validity. The scale also showed modest criterion validity, correlating only with relationship satisfaction concurrently. Patterns of theoretically expected gender differences replicated across samples. Competing hypotheses for the associations between instrumental support and depressive symptoms were also tested, but neither hypothesis was supported due to nonsignificant relations. The ISI-s possesses several advantages over extant instrumental-support scales, most notably in terms of content and discriminant validity.