INTRODUCTION: Postpartum intrauterine device (IUD) insertion is an effective contraception choice for reducing rates of unplanned and short-interval pregnancies. However, timing of placement is controversial, and risk of perforation and expulsion vary with timing. We aim to analyze the cost-effectiveness of postpartum IUD insertion intervals when considering risk of perforation or expulsion. METHODS: A decision-analytic model compared four intervals of postpartum IUD insertion: between 0 and 3 days, 4 days and 6 weeks, 6 and 14 weeks, or 14 and 52 weeks postpartum. A theoretical cohort of 600,000 was calculated using the estimate that 15.3% of postpartum people receive a long-acting reversible contraceptive. Probabilities, costs, and utilities were procured from the literature. Primary outcomes included IUD-related uterine perforation, expulsion, unplanned short-interval pregnancy, termination, stillbirth, ectopic pregnancy, and preterm delivery. The cost-effectiveness threshold was $100,000/quality-adjusted life-year (QALY). RESULTS: IUD insertion between 6 and 14 weeks postpartum was the cost-effective strategy despite having 1,978 and 1,982 additional perforations in intervals between 0–3 days and 14–52 weeks, respectively. All other outcomes were reduced. When compared to the intervals of 0–3 days, 4 days–6 weeks, and 14–52 weeks postpartum, this strategy resulted in 3,054, 282, and 3,816 more QALYs and decreased costs by $91 million, $22 million, and $316 million, respectively. CONCLUSION: Intrauterine device insertion between 6 and 14 weeks postpartum is the cost-effective strategy despite increased risk of perforation. Appropriately counseling patients on the risks and benefits associated with timing of IUD insertion is an important component of postpartum care.