Jeff Irwin serves as Assistant Majority Floor Leader. He represents parts of Ann Arbor, Ann Arbor Township, Lodi Township, Milan Township, and all of Augusta Township, Bridgewater Township, Clinton Township, Macon Township, Manchester, Manchester Township, Milan, Pittsfield Township, Saline, Saline Township, Superior Township, Tecumseh, Tecumseh Township, York Township, Ypsilanti, and Ypsilanti Township.

Senator Irwin is Chair of Housing and Human Services, Chair of Environment, Great Lakes, and Energy (EGLE) Appropriations Subcommittee, Vice-Chair of Joint Capital Outlay Appropriations Subcommittee, and Vice-Chair of Universities & Community Colleges Appropriations Subcommittee.