We study the role of self-promotion and career advice in sustaining gender differences in labor market outcomes. We conduct a pre-registered experiment in which “advisers” advise “workers” to attempt either a more or a less ambitious task. We find that women promote themselves less than men and, as a result, are 12 percentage points less likely to be advised to choose the more ambitious task. This gender gap in advice persists across both quantitative and qualitative self-assessments and is robust to variation in advisers’ information sets—including when advisers observe workers’ actual performance—but is eliminated and even reversed when advisers are informed of the gender gap in self-promotion.