(1) Background: The present study developed and evaluated a personal emotional capital questionnaire (PECQ) for adults that assessed 10 domains of personal emotional capital. (2) Method: Initially, 100 items were created and then administered to students attending Semnan University and Semnan University of Medical Sciences in Iran. Of the 700 questionnaires distributed, 527 were completed in full. Students were sampled using the multi-stage random cluster method. Exploratory factor analyses, Cronbach’s alpha, and test–retest reliability were used to evaluate the scale. (3) Results: The ten components of the PECQ were confirmed. Test–retest correlations after 30 days were high, as was Cronbach’s alpha (0.94). The components highly correlated with overall emotional capital. The PECQ displayed convergent validity as it positively correlated with the Keyes’s Mental Health Continuum—Short Form and students’ GPAs. The PECQ displayed divergent validity as it negatively correlated with measures of depression, anxiety and stress (Depression Anxiety and Stress Scale (DASS21)). Differences in overall PECQ scores and its components were examined for several variables including gender, age, marital and employment status, academic program, and field of study. PECQ scores were not sensitive to the order of administering questionnaires. (4) Conclusion: The results suggest that the PECQ is a valid and reliable measure of personal emotional capital and supports its use in adults.