The purpose of this study is to explore the lived experiences of older single mothers and their co-resident, ever-single daughters with a focus on the meanings of co-residence and the mechanism of their relationships. The participants of in-depth interviews were four pairs of mothers (61-64 years) and their daughters (36-41 years). Two mothers were widows, one was divorced, and one had a husband in a persistent vegetative state. Our thematic analysis revealed that intergenerational co-residence was a comfortable, satisfactory lifestyle for most participants. However, some mothers felt uncomfortable about their daughter’s delayed marriage and their responsibilities for caring for their adult children. The mothers tended to rely on their daughters emotionally, and the daughters relied on their mothers for housework. Most participants viewed the co-resident daughter as a child who was not an adult yet, except for one daughter who financially supported the mother. The participants were concerned that others may view their co-residence negatively because the daughters were not married despite social norms about the appropriate age of marriage. The mothers did not want to be considered a barrier to their daughter’s marriage, and the daughters did not want to be viewed as a child who would abandon their older single mothers. It appeared that the mother-daughter relationship was enmeshed based on the mother’s sense of responsibility for her child and the daughter’s sense of sympathy toward her mother. In this co-dependent relationship context, the daughter’s marriage became a complicated choice both for the mothers and daughters.