Employers’ pay policies can contribute to the gender wage gap if women are less likely to work at high-paying firms or if women negotiate worse wage bargains then men. Analysing data from Portugal’s labour market, this research finds that differences among firms can explain up to 20% of the gender wage gap. Women tend to be employed at less productive firms that offer lower wages to their employees. Moreover, when women are hired by better-paying firms, their wages rise less than men, possibly because they are less effective negotiators. These findings call for renewed attention to equal pay and fair hiring laws.