Chicago Mayor Rahm Emanuel picked Armstrong to replace Bob Pickens, who played for the Chicago Bears in the 1960s.
Emanuel says Armstrong's passion for sports and experience as an executive make him a good choice to serve on the board and help manage the district's 580 parks.
Armstrong was a point guard with the Bulls from 1989 to 1995, and he rejoined the team from 1999 to 2000. After his playing days, he worked for five years in NBA management. He's now an agent for Bulls star Derrick Rose.