A vibrant literature has emerged that explores the economic implications of the sex ratio (the ratio of men to women in the population), including changes in fertility rates, educational outcomes, labor supply, and household purchases. Previous empirical efforts, however, have paid less attention to the underlying channel via which changes in the sex ratio affect economic decisions. This study combines evidence from a field experiment and a survey to document that the sex ratio importantly influences female bargaining power: as the sex ratio increases, female bargaining power increases.