The first years of life and the family context are key to the promotion and protection of children’s health and well-being, emphasizing the need for interventions aimed to support families with young children. This review aimed to explore the effectiveness of early childhood interventions developed for promoting mental health and parenting among families with young children in the Nordic countries. Six electronic databases were systematically searched, and 20 articles covering 16 studies applying various quantitative and qualitative methods met the study inclusion criteria. The studied interventions were assessed as universal health-promoting interventions and health-promoting interventions with elements of prevention. Outcomes of interest encompassed mental health, related risk and protective factors among the parents and/or the children, or child-parent interaction. The results from studies applying statistical methods show significant improvements in parents’ self-efficacy, self-esteem, and parental satisfaction, while few improvements in parents’ social support or parental relationship were identified. Improvements in social support and parental relationships were however reported in qualitative studies. Most quantitative studies reporting on parents’ mental health problems and stress found a significant decrease, and qualitative studies highlighted experienced positive effects on mental health and well-being. The majority of studies reporting on children’s mental health and/or development as well as strengths and difficulties indicated a statistically significant positive development. No significant changes were however found for existing behaviora lproblems. The majority of studies examining parenting strategies and/or parent-child interaction found significant positive changes after the interventions. In sum, although findings are heterogeneous, early childhood interventions show various positive effects on the parenting and mental health of both children and their parents. The fact that different types of initiatives have been developed and implemented can be seen as an advantage, considering the varying needs and expectations of different families.