The Leadership/Teamwork Self-Efficacy Scale has been shown to be an effective tool for measuring interpersonal competence beliefs in science, technology, engineering, and mathematics academic settings. However, little is known about its psychometric properties. The present research explored the measure's longitudinal factor structure in the context of an energy science intervention for high school students. Results of multiple group confirmatory factor analysis yielded evidence of a two-factor structure, as the measure demonstrated strong measurement invariance and excellent test-retest reliability. Results also indicated that latent leadership and teamwork means increased significantly from pretest to posttest, thus also highlighting the efficacy of the intervention in promoting these attributes. Development of leadership and teamwork skills is discussed from trait-based and contextual perspectives.