OBJECTIVES: We examined demographic characteristics and birth outcomes of infants with neonatal abstinence syndrome (NAS) and their mothers in Canada. METHODS: This retrospective, population-based, descriptive cross-sectional study of motherinfant dyads included all singleton live births in Canada (excluding Quebec), from 2005-2006 to 2015-2016 (N 5 2 881 789). Demographic characteristics, NAS, and neonatal and maternal morbidities were identified from delivery hospitalization data (including diagnostic codes). The main composite outcomes were maternal and neonatal mortality and/or severe morbidity, including death and potentially life-threatening conditions in the mother and the infant, respectively. Logistic regression yielded adjusted odds ratios (aORs) and 95% confidence intervals (CIs). RESULTS: The study included 10 027 mother-infant dyads with NAS. The incidence of NAS increased from 0.20% to 0.51%. Maternal mortality was 1.99 vs 0.31 per 10 000 women in the NAS group versus the comparison group (aOR 5 6.53; 95% CI: 1.59 to 26.74), and maternal mortality and/or severe morbidity rates were 3.10% vs 1.35% (aOR 5 2.21; 95% CI: 1.97 to 2.49). Neonatal mortality was 0.12% vs 0.19% (aOR 5 0.28; 95% CI: 0.15 to 0.53), and neonatal mortality and/or severe morbidity rates were 6.36% vs 1.73% (aOR 5 2.27; 95% CI: 2.06 to 2.50) among infants with NAS versus without NAS.