Previous research on psychological contracts has focused on whether or not employees feel their employers have fulfilled the promises made to them. Instead, here we examine how perceptions of the external labor market, particularly about whether present psychological contracts could be replicated elsewhere, influence employees' attachment to their current employers. In a longitudinal study of a diverse employee sample, we found perceptions that psychological contracts could not be replicated elsewhere accounted for a substantial amount of the variance in affective commitment (0.38) and normative commitment (0.29) and a smaller, but significant, amount of the variance in continuance commitment (0.04). We also found significant moderating effects of age, work experience, and career stage on these relationships. The article concludes with implications for psychological contract theory, organizational commitment theory, and management practice. (Contains 3 figures and 1 table.)