The increase in one-person households (OPHs) in the developed world is often seen as the result of a trend in which individualistic values and behaviors are replacing family solidarity. Nordic countries have been identified as frontrunners in this development. In Asia, equally developed countries like Japan retain elements of a strong-family system and an asymmetrical gender regime, simultaneously as they are experiencing rapid increases in OPHs. This article aims to uncover how the demographic and socioeconomic composition of OPHs have developed since the 1990s among working-age women in Sweden and Japan. Our results show that, in particular, civil status and income play different roles for OPH-living in Sweden and Japan. In contrast to Japan, the level of OPHs remained stable over time in Sweden, and even declined among women with high incomes. This suggests that the negative association between family formation and women’s economic activity is temporary and only prevails as long as society has not adapted to the convergence of men’s and women’s socioeconomic roles. The findings are discussed in light of the “second demographic transition” and “dual equilibrium theory”.