The current study tested the hypotheses that (1) psychological adaptations calibrate Openness to Experience to facilitate or deter pursuit of short-term mating, and (2) this calibration varies as a function of mating strategy, physical attractiveness, and sex—individual differences that shift the costs and benefits of alternative personality strategies. Participants completed a personality inventory before and after reading vignettes describing mating opportunities of different durations (short- and long-term) with individuals of differing levels of attractiveness. Among study findings, participants presented with short-term mating opportunities with individuals of average attractiveness exhibited down-regulated Openness relative to those presented with highly attractive mates. Moreover, these effects varied as a function of the interaction between participants’ sex, mating strategy, and attractiveness. These findings are consistent with the hypothesis that evolved psychological mechanisms adaptively calibrate Openness levels in response to short-term mating opportunities. More broadly, they highlight the heuristic value of an evolutionary framework for the study of personality and individual differences.