The aim of this study was to examine contextual antecedents and well‐being indicators associated with children's and adolescents' access to supportive nonparent adults (SNPAs). We conducted secondary data analysis of the 2016 National Survey of Children's Health, a large‐scale caregiver‐reported survey. We analyzed separate subsamples of children (ages 6–11, n = 12,849) and adolescents (ages 12–17, n = 17,628). For both children and adolescents, markers of social advantage (e.g., White race, nonimmigrant families, neighborhood/community capital, access to extracurriculars) increased the likelihood of having SNPAs, according to parent or caregiver reports. Familial factors (e.g., parent participation in school and extracurricular activities) were stronger predictors of SNPA presence for children. Access to SNPAs was negatively associated with social difficulties among children and adolescents and positively associated with curiosity and overall health among adolescents. In conclusion, disadvantage across multiple ecological levels impairs children's and adolescents' access to SNPAs. Having an SNPA may be associated with some aspects of youth well‐being, although causality cannot be inferred in cross‐sectional data.