Family lives have been changed dramatically due to the stay-at-home orders implemented during the coronavirus disease 2019 (COVID-19) outbreak. A variety of factors serve to increase the risk for children and adolescents in developing mental health issues during the prolonged stay-at-home period. The primary aim of this study was to examine a complex conceptual model linking daily routines, parent-child conflict, and indices of psychological maladjustment during the COVID-19 pandemic in a large sample of Chinese children and adolescents. Participants were N = 1,594 children and adolescents (50.6% girls; M age = 13.13, SD age = 1.54) and their mothers, from Zhengzhou in Mainland China. Multisource assessments include youth self-reports of loneliness, depressive symptoms, and perceived conflict with parents during the stayat-home period, as well as maternal reports of their child's daily routines during this time. Among the results, parent-child conflict mediated the relations between daily routines and indices of psychological maladjustment, such that a lack of routine predicted greater parent-child conflict, which in turn was associated with higher levels of loneliness and symptoms of depression. Further, results from multiple group analyses revealed that associations between daily routines and maladjustment were stronger among boys than girls-as well as stronger among primary school children than middle school adolescents. Findings highlighted the importance of maintaining regular routines for children's and adolescents' mental health during the COVID-19 pandemic.