In romantic couples, there is usually an asymmetry in decisional power such that one partner is dominant and the other is subordinate. This study investigated the role of sex, ethnicity, self-assessed social status, personality traits, and power motivation (both explicit and implicit) as potential determinants or correlates of couple dominance in a mixed-sex sample of 50 college students. Through a previously validated questionnaire, participants indicated whether they were dominant or subordinate in their romantic relationship, or whether the latter was egalitarian. Major personality domains, narcissism, psychopathy, borderline, autistic-like traits, and explicit power were assessed through questionnaires. Participants also underwent a Picture Story Exercise to evaluate their implicit motives. Being dominant and having high explicit, but not implicit, power motivation were associated with some psychopathic, narcissistic, and/or borderline traits, while autistic-like traits were associated with being subordinate. Traits such as extraversion, conscientiousness, and honesty-humility had weak associations with couple dominance and/or explicit or implicit power motivation. Our findings have implications for the understanding of dominance dynamics within couples and the relationship between personality traits and power motivation.