Improving access to the choice of postpartum contraceptive methods is a national public health priority, and the need is particularly acute within the Medicaid population. One strategy to ensure individuals have access to the full range of contraceptive methods is the provision of a method prior to hospital discharge following a birth episode. Beginning in 2016, some states changed their Medicaid billing policy, allowing separate reimbursement for intrauterine devices and contraceptive implants to increase the provision of long-acting reversible contraceptive (LARC) methods immediately postpartum (IPP). To assess the association of a change in Medicaid billing policy with use of IPP LARC. The cohort study of postpartum Medicaid recipients in 9 treatment and 6 comparison states was conducted from January 2016 to October 2019. Data were analyzed from August 2023 to January 2024. The primary outcome was use of IPP LARC. The final sample included 1 378 885 delivery encounters for 1 197 287 Medicaid enrollees occurring in 15 states. Mean age of beneficiaries at delivery was 27 years. The IPP LARC billing policy was associated with a mean increase of 0.74 percentage points (95% CI, 0.30-1.18 percentage points) in the immediate receipt of IPP LARC, with a prepolicy baseline rate of 0.54%. The IPP LARC billing policy was also associated with an overall increase of 1.48 percentage points (95% CI, 0.43-2.73 percentage points) in LARC use by 60 days post partum. In this cohort study, changing Medicaid billing policy to allow for separate reimbursement of LARC devices from the global fee was associated with increased use of IPP LARC, suggesting that this may be a strategy to improve access to the full range of postpartum contraceptive methods.