Parents display a highly gendered division of labour: fathers specialize in paid work and mothers take over most domestic work. However, the processes underlying the long-term effect of parenthood on a couple’s time allocation remain obscure, because previous research merely looks at the average effect of having children, neglecting possible interactions with the partners’ absolute and relative resources. More specifically, affluent couples might be able to mitigate the impact of parenthood on time allocation by substituting their domestic work with services purchased in the market. Further, in couples with a female breadwinner prior to parenthood, men might take over the majority of household tasks after children are born. This study tests these hypotheses with data from the German Socio-Economic Panel using fixed-effects regression. The analysis shows that parenthood leads to a long-term increase in women’s housework and childcare time and a pronounced decline in market hours regardless of household income and pre-birth resource constellation. Men’s time use is hardly affected by the birth of children even if they were financially dependent on their partner. These results suggest norms as the main driving force behind long-term dynamics in couples’ time allocation across the transition to parenthood. The article concludes that future research needs to address the interplay of economic and normative factors in shaping time allocation in greater detail, both empirically and theoretically.