The Forum on Regenerative Medicine of the National Academies of Sciences, Engineering, and Medicine convened a two-day virtual public workshop to address knowledge gaps in the understanding of promising approaches to manipulate the immune system and/or the regenerative medicine product to improve outcomes of tissue repair and regeneration in patients. The workshop, titled "Understanding the Role of the Immune System in Improving Tissue Regeneration," explored the role of the immune system in the success or failure of regenerative medicine therapies. Participants considered potential strategies to effectively "prepare" patients' immune systems to accept regenerative therapies and increase the likelihood of successful clinical outcomes and also discussed risks associated with modulating the immune system. This Proceedings of a Workshop highlights the presentations and discussions that occurred during the workshop.