<p>The formation of secure parent–child bonds in early life, hereto referred to as early relational health, plays a central role in healthy development. However, the evidence on how early relational health ‘gets under the skin’ to impact the developing brain remains unclear. Here, we provide a scoping review of the extant literature and synthesize evidence on the link between relational health from conception to age three and subsequent brain structure, function, and connectivity. Literature searches in MEDLINE, PsycINFO, and Embase databases yielded 7156 studies. Screening of studies was conducted on the Living Knowledge System (an AI-assisted screening tool), which resulted in 79 studies being included in the review. Results were synthesized based on the type of relational health examined, type of imaging modality (e.g., electroencephalogram, structural, and functional magnetic resonance imaging), and developmental stage. We identified studies of the relationship between early relational health and brain structure, function, and connectivity that spanned from childhood to young adulthood, with no research beyond this age period. There was evidence for early relational health to be associated with patterns of brain activation that may reflect the experience of more positive emotions and reduced risk for psychopathology. However, few studies examined longitudinal changes in brain structure, function, and connectivity. Even fewer have examined relational health beyond the mother–infant bond. Future research is needed to improve understanding of the impact of relational health on brain development and to ascertain whether such impacts reflect a mechanism linking relational health with health and wellbeing across the lifespan.</p>