BACKGROUND:The association between developmental adversity and children's functioning is complex, particularly given the multifaceted nature of adverse experiences. The association between the timing of experience and outcomes is underresearched and clinically under-appreciated. We examine how the timing of both adverse (including potentially traumatic) events and relational poverty are associated with developmental outcomes. METHOD:Clinicians using the Neurosequential Model of Therapeutics (NMT), an approach to clinical problem solving, reported on the timing of children's developmental experiences, their degree of current relational health, and current functioning in key brain-mediated domains (N = 3523 6- to 13-year-old children). A regularized hierarchical model produced stable and generalizable estimates regarding associations between the timing of experiences across four developmental periods: Perinatal (0-2 mos), Infancy (2-12 mos), Early Childhood (13 mos to 4 years), and Childhood (4 to 11 years) and current functioning. RESULTS:Perinatal developmental experiences were more strongly associated with compromised current functioning than such experiences occurring during other periods. Perinatal relational poverty was a stronger predictor than perinatal adversity. During subsequent developmental periods, the influence of relational poverty diminished, while the influence of adversity remained strong throughout early childhood. Current relational health, however, was the strongest predictor of functioning. CONCLUSION:Findings expand the understanding of the association between the timing of adversity and relationally impoverished experiences and children's functioning. Although early life experiences are significantly impactful, relationally enriched environments may buffer these effects.