Research from the United States consistently shows that female-dominated occupations tend to yield lower wages than male-dominated occupations. Using detailed occupational data and multilevel modelling techniques, this study analyses size and causes of this occupational gender wage gap in the Netherlands. Main findings are that both men and women earn lower wages, when employed in female-dominated occupations. This indicates the significance of gender in the Dutch labour market, especially since overall levels of wage inequality are relatively small in the Netherlands compared to countries like the United Kingdom and the United States. The allocation of women to occupations with lower levels of responsibility accounts for this occupational wage gap. In addition, a large within-occupation sex gap in wages is found. Even when men and women work in the same occupation, women earn significantly lower wages than men. This indicates the presence of an undervaluation of female labour in the Dutch labour market.