Mercer, along with the rest of the Critical Role cast, has frequently supported 826LA, a non-profit organization dedicated to supporting students ages 6-18 with their creative and expository writing skills. This has included charity streams and other fundraising efforts.

Matthew Mercer and the Critical Role cast have participated in various charity streams and events, raising money for organizations such as Red Nose Day, Extra Life, and the Pablove Foundation. These streams often involve playing games, interacting with fans, and offering unique incentives for donations.

Mercer is a vocal advocate for inclusivity and representation in gaming and entertainment. He uses his platform to promote diverse voices and stories and create a welcoming community for all fans.