Using data from the European Social Survey (2002-14), this paper explores the effect of union membership on support for redistribution. We hypothesize that the wage-bargaining practices of unions promote egalitarian distributive norms among low-wage and high-wage union members alike and that distributive norms in turn lead union members to support redistribution. Consistent with our expectations, the empirical analysis shows that the solidarity effect of union membership is strongest when unions encompass a very large share of the labor force or primarily organize low-wage workers. We also show that low-wage workers have become a significantly less important union constituency in many European countries over the time period covered by our analysis.