The benefits of routines for children have been consistently demonstrated in previous literature. However, factors that may confer risks for child routines have seldom been examined, particularly in families where parents and grandparents co-care the children. This study aimed to investigate the associations of parents’ and grandparents’ depressive symptoms with preschoolers’ daily routines in Chinese three-generation families and to determine whether household chaos mediated or moderated the associations. The participants were from 171 urban three-generation families where mothers, fathers, and grandmothers (97 paternal and 74 maternal) were primary caregivers. Mothers, fathers, and grandmothers reported their depressive symptoms at Wave 1; at Wave 2 (during the COVID-19 pandemic), caregivers reported household chaos and child routines. The results revealed that child routines were negatively predicted by parents’ joint depressive symptoms rather than grandmothers’ depressive symptoms. In the associations, household chaos acted as a mediator rather than a moderator. Specifically, household chaos marginally mediated the associations between parents’ and grandmothers’ depressive symptoms and child routines only in maternal three-generation families. These findings suggest that in three-generation families, caregivers with more depressive symptoms may elicit more chaotic family environments, which may in turn compromise their children’s daily routines.