Women are underrepresented in political and business decision-making bodies across the world. To investigate the causal effect of gender representation on multilateral negotiations, we experimentally manipulate the composition of triads in a majoritarian, divide-the-dollar game. First, we find that inclusive splits and unanimous agreement rates are highest in all-female groups and lowest in all-male groups suggesting that female representation increases fairness. Second, we document a robust gender gap in earnings, driven largely by the exclusion of women from coalitions rather than differential shares within coalitions. Interestingly, we find that distinct bargaining dynamics can underlie the same inequitable outcomes: While gender-biased outcomes are sometimes caused by outright discrimination, they can also be driven by more complex dynamics related to gender differences in bargaining strategies. These different dynamics manifest in mixed-gender coalitions being less stable when the excluded party is male rather than female.