The present research tested the hypothesis that perception of others' self-control is an indicator of their trustworthiness. The authors investigated whether, in interactions between strangers as well as in established relationships, people detect another person's self-control, and whether this perception of self-control, in turn, affects trust. Results of 4 experiments supported these hypotheses. The first 2 experiments revealed that participants detected another person's trait of self-control. Experiments 3 and 4 revealed that participants also detected the temporary depletion of another person's self-control. Confirming the authors' predictions, perceived trait and state self-control, in turn, influenced people's judgment of the other person's trustworthiness. In line with previous research, these findings support the positive value of self-control for relationships and highlight the role of perceived self-control for the development of a fundamental relationship factor: trust. © 2011 American Psychological Association.