Abstract Background To understand how individual differences in mental well-being emerge for children and adolescents, it is important to understand the amenable factors in the context in which the development takes place - that is, for children, primarily in the family and in school. There is a notable gap in the research exploring the positive impacts of school factors on parent-child dyads and their mental well-being, and if there are any associations between school engagement and the mental well-being of parents and their children. Methods Data from 307 parent-child dyads were included in the study, the data stemming from a Finnish l research project (CONSENSUS) encompassing longitudinal survey data collection among both children in grades 4-6 and their parents. By exploring bivariate correlations and using the Actor-Partner Interdependence Model (APIM), the present study aims to investigate actor and partner effects of school engagement and mental well-being among parents and their child in grade 4-6. Results Preliminary results show that there are statistically significant correlations between parents’ and their children’s mental well-being, but that there are no significant correlations between children’s school engagement and parental school engagement. Further, statistically significant actor effects emerge between children’s school engagement and mental well-being, and between parental school engagement and mental well-being. Conclusions By clarifying the interaction between school engagement and mental well-being in parent-child dyads, this study not only contributes to the theoretical understanding of these constructs but also offers insights that can inform future development of mental well-being promotion interventions aimed at families and educational settings in Finland and elsewhere. Key messages • This study offers an innovative exploration of the links between mental well-being and school engagement among 274 Finnish parent-child dyads. • Results show various interactions between school engagement and mental well-being among the parent-child dyads, with implications for interventions intended to support well-being in families.