We argue that in the Netherlands, due to the growth of part-time work, work norms have declined. The mechanism behind this norm change is in the changed organization of family life. The increased labour market participation of women has put the traditional organization of family life under pressure. Working mothers in the Netherlands opt for part-time jobs, thus sacrificing career opportunities for family life. Working fathers also have to trade-off hours, because a greater contribution to family life is expected from them. This implies that work norms are supported less by both women and men in their redefined roles than in their traditional roles. The hypotheses that follow from this argument are tested in multilevel regression analysis on the OSA Labour Supply Panel surveys for the period 1988–2002. The tests show that part-time working women and their partners adhere less to the work obligation norm than breadwinners and housewives. Adherence to the work obligation norm among parents has decreased with the growth of part-time work. Among non-parents, support for the norm has decreased too, but less than among parents. Our analyses show that, due to the growth of part-time work, the traditional division of labour is no longer predominant, and, as a result, the traditional work ethic is declining.