Despite the traditional sentiment that protean and boundaryless career attitudes indicate a decline in organizational commitment, little empirical evidence is available. The present study examined the relation of protean and boundaryless career attitudes to organizational commitment and whether the perceived supervisor support moderated these relationships. The results based on data from 380 employees demonstrate that organizational mobility preference is negatively related to all three dimensions of organizational commitment. Self-directed career management is positively related to affective and normative commitment and negatively related to continuance commitment, while values-driven career orientation is negatively related to normative commitment. Moreover, there is no significant evidence provided for a moderating effect of perceived supervisor support on the relationships between protean and boundaryless career attitudes and organizational commitment. Perceived supervisor support has only a main effect on affective and normative commitment. (Contains 2 tables.)