Selected by the Chicago Bulls in the first round of the 1989 NBA draft,[1] the 6'2" (1.88 m) Armstrong helped the team return to the Eastern Conference Finals after compiling 55 regular season victories in 1990.

In 1992, Armstrong averaged double-digit scoring while coming off the bench behind longtime starter John Paxson to help the Bulls win 67 games and their second straight title.

Armstrong finished third in scoring again in 1995 as the Bulls posted a 47–35 record, and with Jordan, Scottie Pippen and Toni Kukoč, led the team to the second round again.

He also played 10 games for the Hornets in the 1999 season before being traded to the Los Angeles Lakers, alongside J.R. Reid and Glen Rice, for Elden Campbell and Eddie Jones.

Armstrong stepped into Chicago's front office as a special assistant to Vice President of Basketball Operations Jerry Krause.

He also serves as an agent for Bismack Biyombo, Emmanuel Mudiay, Donatas Motiejūnas, JaVale McGee,[6] Denzel Valentine, and Josh Jackson.