Coalitional mate retention (CMR) occurs when individuals request assistance from a friend to minimize the risk of partner infidelity. We secured reports from men and women in a committed, heterosexual relationship to investigate associations between CMR requests and the sex and personality traits of individuals who request CMR and the sex of their friends. Consistent with our hypothesis, individuals scoring higher in Honesty–Humility requested CMR less frequently. We also documented that individuals higher in Extraversion and lower in Conscientiousness requested CMR more frequently. We address limitations of the research and future research directions, including tests of the hypothesis that CMR involves duplicitous behaviors that are less typical of individual mate retention.