BackgroundPrevious evidence has shown how experiences within childhood, such as parenting and socioeconomic conditions, are associated later on in life with adult mental well-being. However, these studies tend to focus on childhood experiences in isolation, and fewer studies have investigated how multiple aspects of the childhood environment, including both socioeconomic and psychosocial aspects, are associated with adult positive mental well-being. Using data from three British birth cohort studies, we investigated how prospective measures of the childhood environment up to the age of 16 years were associated with midlife adult mental well-being and whether similar associations were replicated across different generations.MethodsChildhood environment comprised socioeconomic circumstances, psychosocial factors (child-rearing and parenting, family instability) and parental health. The Warwick-Edinburgh Mental Wellbeing Scale, a validated instrument measuring both hedonic and eudaemonic aspects of well-being, was administered in mid-life. We modelled associations between childhood environment domains and well-being.ResultsDespite changes in social context in all three studies, poorer quality parent–child relationships and poor parental mental health were strongly and independently associated with poorer adult mental well-being. Socioeconomic circumstances were also associated with adult mental well-being, but the association was weaker than for the measures of parenting or parental mental health.ConclusionThese findings confirm that parenting and parental mental health, as well as socioeconomic circumstances, are important for adult mental well-being. Interventions in early childhood aimed at reducing socioeconomic adversity and offering support to parents might be warranted, to enhance adult mental well-being later on in the life course.