One of the key features of Vietnamese family organization is patrilocality—the preference of married couples to coreside with the husband's parents. With data drawn from a retrospective survey of persons in 1,855 households in the largest province in the Red River Delta in northern Vietnam, we found that more than 75% of married respondents reported having lived with the grooms' family after marriage. The proportion of newly married couples that follow the patrilocal custom appears to have increased in recent decades, although the average duration of coresidence has declined. Some aspects of modernization, especially nonagricultural occupations and later age at marriage, contribute to a lower incidence of intergenerational coresidence, but the underlying cultural preference to live with the grooms' parents immediately after marriage appears to have become stronger in Vietnam. In contrast to some features of traditional family life that conflict with modernity, intergenerational coresidence can be quite functional in modernizing societies.