At age 22, Mitchell recognized overdevelopment in Staten Island to be a problem and worked to rezone his neighborhood of Barrett Park to prevent such unnecessary expansion.

Mitchell served as chief of staff and General Counsel to former councilman (later Congressman) Mike McMahon for seven years.

[3] He was defeated in his bid for re-election during the September 2009 Democratic primary by a community activist, Debi Rose.

[5] Prior to being elected to the New York City Council, Mitchell had also worked with and served on the boards of many local charities and community groups including the Dr. Theodore A. Atlas Foundation (named after the physician father of boxer Teddy Atlas), The Staten Island Zoological Society, The Children's Aid Society at Goodhue Center and the Staten Island Film Festival.

He has received service awards from United Activities Unlimited, Warren Jacques Memorial Committee and the North Shore Democratic Club.