Background: Supporting undergraduate students in science, technology, engineering, and mathematics (STEM) has been a persistent need. However, assessing the impact of support efforts can prove challenging as it is difficult to operationalize student support and subsequently monitor the combined impacts of the various supports to which students have access simultaneously. Purpose/Hypothesis: This paper describes the development of the STEM student perspectives of support instrument (STEM-SPSI) and explores how perceptions of student support constructs vary across engineering students. Design/Method: Following best practices for instrument development, forming the STEM-SPSI consisted of an iterative cycle of feedback from various STEM stakeholders and two rounds of pilot testing with students at multiple institutions. We employed factor analysis to identify student-support constructs and conduct validation procedures on the instrument. Results: Results suggest that student support can be conceptualized as a combination of 12 constructs. The STEM-SPSI can help engineering educators evaluate their student-support mechanisms at an academic-unit level. Conclusions: The practical contribution of the STEM-SPSI is to assist colleges in monitoring the extent to which their portfolio of support mechanisms is perceived as helpful by undergraduate students. This work makes a theoretical contribution to the model of cocurricular support that undergirds the instrument by producing empirical evidence for its constructs.