This article looks at the relationship between psychological contract breach and voluntary turnover among newcomers, using supervisor trustworthiness as a mediator and negative affectivity as a moderator. Relying on data from 243 newcomers, psychological contract breach was found to be negatively related to the three dimensions of supervisor trustworthiness, i.e., ability, benevolence, and integrity. Supervisor integrity further mediated a positive relationship between psychological contract breach and voluntary turnover measured 8 months later. Psychological contract breach interacted with negative affectivity such that it was less negatively related to dimensions of supervisor trustworthiness at high levels of negative affectivity. The indirect relationship of psychological contract breach to voluntary turnover as mediated by supervisor integrity was also weaker at high levels of negative affectivity. We discuss the implications of these findings for research and practice.