BACKGROUND: Parental postpartum co-morbid anxiety and depression negatively impact personal well-being, family dynamics, and child developmental outcomes. This study investigates the prevalence of co-morbid anxiety and depression in both mothers and fathers during the first 2 years postpartum in China, and to explore its associations with parental family support, maternal health-related quality of life (HRQoL), and child development. METHODS: This cross-sectional study was conducted in China, involving families with children aged 0-2 years who participated in community child health care. Data were collected via questionnaires administered to parents by pediatricians and nurses at community health service (CHS) centers. Path analysis was utilized to test the hypothesized model, which links parental co-morbid anxiety and depression to parental family support, maternal HRQoL, and child development. RESULTS: A total of 2073 pairs of both parents who completed the survey were included in the final analyses. The prevalence of maternal and paternal co-morbid anxiety and depression, was 5.7 % and 4.4 %, respectively. Among mothers, the prevalence ranged from 4.3 % to 6.5 % within the first 6 months, and 7.9 % in the second year. After adjusting for covariates, severe family dysfunction was significantly associated with maternal and paternal co-morbid anxiety and depression. The path analysis showed that maternal co-morbid anxiety and depression were directly associated with child development and maternal HRQoL. CONCLUSIONS: These findings highlight the importance of prioritizing family support, addressing both depression and anxiety, involving both parents and extending support beyond the first year postpartum.