Modelling fertility decline in post-industrial populations in the context of life history theory has allowed us to better understand the environmental pressures that shape reduced family size. One such pressure, which has received relatively little attention from ecologists, is the movement of women into the labour market. Analyses of effects of employment on fertility in contemporary developing or post-demographic transition populations are limited by the widespread use of modern contraceptives: while uptake of these methods may be a mechanism by which reduced fertility is enacted, their use may obscure effects of employment on fertility. Here, we investigated the impact of women’s employment on family size during a period of the movement of women into the workforce but prior to the use of modern contraceptives. We analysed the effects of women’s employment on family size using census records from 1901 for a regional-level analysis of parishes in Scotland, and for 1851−1901 for an individual-level analysis of the Scottish city of Dundee. Women in employment had fewer children than those not in employment. Income was inversely related with family size, and this was independent of the effects of women’s employment on family size. We suggest that female employment contributes to the evolution of smaller family sizes and that this takes place in the context of prevailing and emerging gender roles, and in interaction with opportunities for employment and wealth.