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 "e;Understanding the Role of the Immune System in Improving Tissue Regeneration,"e; explored the role of the immune system in the success or failure of regenerative medicine therapies. Participants considered potential strategies to effectively "e;prepare"e; 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.