This paper describes the results of a research study analyzing the challenges of the adoption of open source integrated library systems (OSS ILSs) among U.S. libraries. The research team surveyed 73 libraries of all types currently using proprietary ILSs about their satisfaction with their ILS, whether they have considered migrating to an OSS ILS, and some of the changes that would need to occur inside and outside of the libraries to facilitate migration to OSS ILSs. The results show that most of the libraries surveyed have considered migrating to OSS ILSs. The most common reason for considering migration is the cost savings of OSS ILSs compared to proprietary ILSs. The most common issues libraries cited as reasons not to migrate to OSS ILSs include lack of in‐house technical staff and expertise and perceived lack of OSS ILS technical support. This paper contributes to the field by discussing some specific challenges libraries associate with OSS ILSs. This research will help libraries in the OSS ILS community to better address these challenges and encourage OSS ILS adoption.