This work investigates the interaction between cultural norms and neighborhood characteristics, in the context of the gender gap in math. Using high-quality Swedish administrative data, I estimate the effect of mothers' country-of-origin gender norms on the gender gap in math among second-generation immigrant siblings and exploit a refugee placement policy to obtain random variation in regional characteristics. I find that the sibling gender gap in math increases with cultural gender norms, such that girls with mothers from more gender-traditional cultures perform worse compared to their brothers, but that local labor market gender equality can completely mitigate this cultural norm effect.