Based on arguments of the social exchange theory (SET) and person-organization fit (P-O Fit), the environment can affect personality expression through behaviors and human perception of the environment. This research develops and tests two key assumptions: (1) individuals with proactive personality (PP) show proactive behavior (PB), particularly problem prevention behavior (PrP), through person-organization value congruence (POV), and person-supervisor value congruence (PSV); (2) the strength of the process of demonstrating problem prevention behavior depends on the perceived organizational support (POS) of the staff. Survey results from 715 employees and supervisors at hospitals in Vietnam show that (1) POV and PSV have an intermediary role between PP and PrP, (2) Intermediate effects of POV and PSV in the relationship between PP and PrP are moderated by POS. Specifically, the intermediate effect of POV, PSV is stronger for employees with high POS and lower for employees with lower POS. These findings provide a new perspective on understanding mechanisms to enhance employee’s PrP. As a result, the theoretical, practical implications and limitations of the study are also discussed.