ObjectiveTo explore the association between early essential newborn care (EENC) policy, practice and environmental interventions and breastfeeding outcomes.DesignCross-sectional observational study.Setting150 national, provincial and district hospitals implementing EENC in eight countries in East Asia and the Pacific.Participants1383 maternal interviews, chart reviews and environmental assessments during 2016 and 2017.Main outcome measuresExclusive breastfeeding (EBF), that is, feeding only breastmilk without other food or fluids since birth and before discharge, and, early breastfeeding initiation, that is, during skin-to-skin contact (SSC) with the mother without separation.ResultsFifty-nine per cent of newborns initiated breastfeeding early and 83.5% were EBF. Duration of SSC showed a strong dose–response relationship with early breastfeeding initiation. SSC of at least 90 min was associated with 368.81 (95% CI 88.76 to 1532.38, p<0.001) times higher early breastfeeding. EBF was significantly associated with SSC duration of 30–59 min (OR 3.54, 95% CI 1.88 to 6.66, p<0.001), 60–89 min (OR 5.61, 95% CI 2.51 to 12.58, p<0.001) and at least 90 min (OR 3.78, 95% CI 2.12 to 6.74, p<0.001) regardless of delivery mode. Non-supine position (OR 2.80, 95% CI 1.90 to 4.11, p<0.001), rooming-in (OR 5.85, 95% CI 3.46 to 9.88, p<0.001), hospital breastfeeding policies (OR 2.82, 95% CI 1.97 to 4.02, p<0.001), quality improvement mechanisms (OR 1.63, 95% CI 1.07 to 2.49, p=0.02) and no formula products (OR 17.50, 95% CI 5.92 to 51.74, p<0.001) were associated with EBF.ConclusionEENC policy, practice and environmental interventions were associated with breastfeeding outcomes. To maximise the likelihood of early and EBF, newborns, regardless of delivery mode, should receive immediate and uninterrupted SSC for at least 90 min.