While earning his degree in political science at the University of Michigan, Irwin worked for the Michigan League of Conservation Voters and as a legislative aide to former-State Senator Alma Wheeler-Smith. He proudly served on the Washtenaw County Board of Commissioners from 1999 to 2010, where he was instrumental in instituting a living wage policy, extending health insurance for uninsured workers and protecting our natural resources.

Then, from 2011 to 2017 , Irwin represented the City of Ann Arbor in the Michigan House of Representatives. He helped pass Michigan's Medicaid expansion and led the charge to protect drinking water from high levels of toxic, dangerous chemicals, including 1,4-dioxane. Irwin also introduced and supported legislation that supported better funding for education, protected our environment from polluters and created jobs.

As a state senator, Irwin has introduced legislation tightening regulations against polluters, ensuring our schools are properly screening students for dyslexia and getting them the help they need, allowing more juvenile offenders to seal their records, expunging all cannabis-related offenses, banning PFAS in food packaging and dramatically expanding the Earned Income Tax Credit.

He lives in Ann Arbor with his wife, Kathryn, and their two children, Sylvia and Mackinac.