After graduating from law school, Barber served as an assistant district attorney for New York County from 1977 to 1981. In 1981, Barber joined the Boston-based law firm of Looney &amp; Grossman, becoming a partner in 1985 and serving as managing partner from 2001 to 2003. His law practice focused on start-up companies and commercial litigation. During the 2008 United States presidential election, Barber was a fundraiser and frequent donor to the Barack Obama 2008 presidential campaign. Barber was a member of the Obama for America National Finance Committee.