While in college Mitchell served as a White House intern under the Clinton Administration, and as a law clerk for the NAACP Legal Defense Fund and later with the Maryland Public Defender's Office and the Democratic Senatorial Campaign Committee. In 1995, Mitchell returned to Boys' Latin School, to teach United States, African-American, and Maryland history. Additionally, he was also the junior varsity basketball head coach. That same year, he was elected to the Baltimore City Council, serving as Chairman of the Education and Human Resources Committee and Vice-Chairman of the Judiciary Committee.