This study examined the construct validity of scales measuring dual commitment—organizational commitment and union commitment. Using the Organizational Commitment Questionnaire and the Scale of Union Commitment, the conceptual independence of organizational commitment and union commitment was investigated. The results show that union commitment is accepted as a concept distinct from organizational commitment, and that organizational commitment is a relatively stable concept, consistent with findings from other studies. However, among the components of union commitment, willingness to participate in union activities was accepted as the same concept regardless of the sample, although differences in its intensity were observed.