This brief examines ACA marketplace participation by insurers that participated in Medicaid but not in private insurance markets prior to the ACA. Our focus is on the potential hurdles for increased participation from Medicaid insurers. Premiums tend to be lower in regions where Medicaid insurers participate, so increasing Medicaid insurer participation has the potential to provide nongroup market consumers more affordable coverage options. We interviewed insurers and associations around the country to identify reasons why Medicaid insurers might not be entering the marketplaces and any potential assistance that states could provide to entice further participation. We identified distinct differences between traditional commercial insurers and Medicaid insurers that likely are contributing to lack of participation. Additionally, we inquired about the Medicaid insurers’ interest in Medicaid “buy-in” proposals. We found that Medicaid insurers are intrigued by the prospects of a Medicaid buy-in program, but they are waiting to evaluate fully detailed plans when they become available.