Gender differences in wage negotiations is a popular explanation for why the gender gap in pay persists in the United States. In this study, we use data from an artificial wage negotiation experiment (N = 330) to interrogate the gender-negotiation link, and to test whether gender role attitudes (GRAs) moderate this association. Our experiment yields three principal discoveries. First, men are more likely to select into negotiations than women, but this effect varies by GRAs. As GRAs become more traditional, men enter negotiations at a much higher rate than women, but for non-traditional GRAs we observe no gender differences in selection. Second, while men and women are proficient at knowing when to negotiate, men and women are much less proficient when they harbor traditional GRAs. Third, profits are equivalent for men and women, and traditional men are no more effective than women—regardless of their GRAs—at securing higher profits. Our findings suggest that traditional women should “lean-in”, and that traditional men should “lean-out”.