Based on person-organization fit and social exchange theory, this study investigates the effect of the needs-supplies fit of developmental job experience (DJE) on proactive behavior and explores the mediating role of affective organizational commitment (AOC). A lagged survey design in two-wave was used, and hypotheses were tested using polynomial regression and response surface analysis. The results show that different fit combinations between individuals’ needs for DJE and organizations’ supplies affect proactive behavior. Employees engaged in more proactive behavior when high-high fit (vs. low-low fit) and undersupply (vs. oversupply) were present. Furthermore, the effect of the needs-supplies fit of DJE on the different foci of proactive behavior is different. As hypothesized, the relationship between the needs-supplies fit of DJE and proactive behavior is mediated by AOC. The results of this study can deepen researchers’ understanding of the role of DJE in employees’ organizational, interpersonal, and personal proactive behavior and provide support for the effective mechanisms of DJE on proactive behavior based on social exchange theory and person-organization fit theory.