Although work is a core part of life, the direction of influence from personality to work has typically been conceived as only unidirectional. The present study aims to contribute to the literature by considering reciprocal relations between personality and occupational characteristics, drawing on current perspectives from personality psychology (i.e., the social investment principle) and using a well-established framework to conceptualize career development (i.e., Holland's RIASEC theory). For this purpose, a longitudinal cohort of college alumni (N = 266) was tracked across a substantial and significant period in their professional career. Big Five personality traits and RIASEC occupational characteristics were assessed at the career start and 15 years later when their careers had unfolded. A combination of observed and latent variable analyses were used to disentangle the longitudinal and reciprocal relations between traits and occupational characteristics. Our results indicate that personality shapes and is shaped by our vocational experiences, suggesting that work can be a source of identity. The implications for theory and research on personality in the industrial and organizational literature are discussed alongside a number of practical implications for organizational and counseling settings.