Background: The use of oral opioids as standard treatment after cesarean delivery has been linked to persistent use in opioid-naïve women in the USA. In Denmark, the use of opioids after cesarean delivery is typically restricted to in-hospital use. The aim of this study was to estimate the incidence of persistent postpartum opioid use in Denmark and compare it by mode of delivery. Methods: This was a national cohort study of all women giving birth in Denmark in 2016, with one-year follow-up. Data from Danish registries were retrieved and combined using each woman's unique identification number. Persistent use of opioids was defined as ≥3 redeemed opioid prescriptions 31–365 days postpartum. Results: A total of 62 520 births were included in the cohort: 49 859 vaginal deliveries, 5310 intrapartum cesarean deliveries, and 7351 pre-labor cesarean deliveries. For all births, persistent postpartum opioid use occurred in 85 (140 in 100 000) women of whom 36 (42%) had opioid use during pregnancy. The incidence of persistent opioid use was highest in the pre-labor cesarean delivery cohort (n=27; 360 in 100 000) and lowest in the intrapartum cesarean delivery cohort (n=3, 60 in 100 000; P<0.001). Women taking opioids during pregnancy were at increased risk of persistent opioid use (odds ratio 63.3; 95% CI 43.9 to 91.4). Conclusions: Women giving birth in Denmark, where use of post-discharge opioid treatment is generally restricted, have a low risk of developing persistent use of opioids, with very few women seeking additional analgesic treatment from their general practitioner.