This study examines the longitudinal relationships between job resources, personal resources, and work engagement, based on Conservation of Resources (COR) theory. The study involved 163 employees followed over an average period of 18 months. Structural equation modeling analyses supported the hypotheses that job resources, personal resources, and work engagement are reciprocal over time. Specifically, T1 job and personal resources positively related to T2 work engagement, and T1 work engagement positively related to T2 job and personal resources. The reciprocal model, which showed mutual relationships among job resources, personal resources, and work engagement, fit the data best. These findings support the assumption that various types of resources and well-being evolve into a cycle that determines employees' successful adaptation to their work environments.This study examines the longitudinal relationships between job resources, personal resources, and work engagement, based on Conservation of Resources (COR) theory. The study involved 163 employees followed over an average period of 18 months. Structural equation modeling analyses supported the hypotheses that job resources, personal resources, and work engagement are reciprocal over time. Specifically, T1 job and personal resources positively related to T2 work engagement, and T1 work engagement positively related to T2 job and personal resources. The reciprocal model, which showed mutual relationships among job resources, personal resources, and work engagement, fit the data best. These findings support the assumption that various types of resources and well-being evolve into a cycle that determines employees' successful adaptation to their work environments.