Previous research indicates that Euro-American women are more upset by imagining their male partners committing homosexual infidelities than heterosexual ones. The present studies sought to replicate these findings and extend them to two non-Western cultures wherein masculine men frequently engage in sexual interactions with feminine third-gender males. Across six studies in three cultural locales, women were asked to rate their degree of upset when imagining that their partner committed infidelity that was heterosexual in nature, as well as infidelity that was homosexual. In two Canadian undergraduate samples, women reported greater upset at imagining partner infidelity with a female, whereas a community sample of middle-aged women reported equal upset across infidelity types. Samoan women reported substantially less upset at the thought of partner infidelity with a third-gender male than with a female. Istmo Zapotec women reported equal upset toward infidelity with a female or a third-gender male, whereas a second Zapotec sample reported slightly greater upset at the thought of infidelity with a muxe. Results illustrate how cultural contexts moderate the degree to which same-sex infidelity scenarios are upsetting to women.