Objective: This study examined the effect of immediate versus delayed postpartum levonorgestrel IUD insertion on breastfeeding outcomes. Methods: This noninferiority randomized controlled trial conducted at two sites assigned healthy pregnant women who desired a levonorgestrel IUD and planned to breastfeed 1:1 to immediate postpartum insertion (immediate group) or insertion four to 12 weeks postpartum (delayed group). Data are reported using per-protocol analysis per noninferiority standards. The primary outcome was breastfeeding continuation at eight weeks; the study was powered to detect a 15% noninferiority margin between groups. The secondary outcome was time to lactogenesis using a validated measure. Only the data analysis team was blinded to the intervention. Results: The immediate and delayed groups included 132 and 127 women, respectively. Report of any breastfeeding at eight weeks in the immediate group (79%, 95% CI 70%-86%) was noninferior to that of the delayed group (84%, 95%CI 76%-91%). Time to lactogenesis (mean ± SD) in the immediate group, 65.3 ± 25.7 hours, was noninferior to that of the delayed group, 63.6 ± 21.6 hours; the mean difference was 1.7 hours, 95% CI -4.8 to 8.2 hours. A total of 24 expulsions occurred in the immediate group compared to 2 expulsions in the delayed (19% versus 2%, p<0.001). Conclusion: Noninferior breastfeeding outcomes suggest that immediate postpartum insertion is an acceptable option for women planning to breastfeed and use the levonorgestrel IUD; however, expulsion rates are higher.