Mohn, as president of the Heartland Alliance, has been a key part of work on behalf of people with AIDS and civil-rights for the LGBT community.

He is a board member of the Center for Middle Eastern Studies/NorthPark University, the National Immigration Forum, the City of Chicago Human Relations Commission, and Global Chicago. He supports Dignity/Chicago and various church and human-rights groups. He is a founder of the Illinois Coalition for Immigrant and Refugee Rights; the Chicago Coalition for the Homeless; Centro Romero; National Immigrant Justice Center; and the Kovler Center for Treatment of Survivors of Torture.