Women tend to be more jealous in situations where they could lose investment or commitment from their partners compared to men who are more jealous when they could lose sexual exclusivity, consistent with evolutionary explanations. To test this idea in the context of extramarital friendships, we predicted that jealousy in response to a spouse’s new friend would vary based on the individual’s gender, the friend’s gender, and the friend’s attractiveness (since women’s mate value is based more on beauty than men’s). In the current study, we assigned married individuals to read a hypothetical scenario that varied across these three factors. Afterward, they completed the Multidimensional Jealousy scale which assesses overall, cognitive, behavioral, and emotional jealousy. The 3-way interaction was significant, but only for the cognitive subscale. We found a significant 2-way interaction between participant gender and friend gender for all jealousy subscales. We further documented that women were significantly more jealous than men overall, consistent with our prediction. Although most prior research has focused on jealousy at the emotional level, our research shows that there are interesting gender differences across dimensions of jealousy.