[2] As a coach, Cooper led the Los Angeles Sparks of the Women's National Basketball Association (WNBA) to two championships and the Albuquerque Thunderbirds to one NBA G League title.

In Cooper's senior season, he was named a first-team All-American by the United States Basketball Writers Association.

Selected by the Los Angeles Lakers in the third round of the 1978 NBA draft with the 60th overall pick,[8] Cooper became an integral part of their Showtime teams of the 1980s with his defensive skills.

Until 2024, Cooper and Norm Van Lier had the most defensive selections of any player to not be inducted into the Naismith Basketball Hall of Fame.

"[12] Leaving the team after the 1989–90 season, he was ranked among the club's all-time top 10 in three-point field goals (428), games played (873), total minutes played (23,635), steals (1033), blocked shots (523), assists (3,666), defensive rebounds (2,028), offensive rebounds (741), and free throw percentage (.833).

Cooper then played for the 1990–91 season in Italy for Pallacanestro Virtus Roma in the Italian Serie A, averaging 15.8 points, 6.1 rebounds, 1.9 steals, 1.8 assists, and 0.3 blocks per game.

Following Cooper's playing career, he served as Special Assistant to Lakers' general manager Jerry West for three years before joining the Lakers' coaching staff in March 1994 under Magic Johnson, then with Del Harris from 1994 to 1996. Cooper became an assistant coach of the WNBA's Los Angeles Sparks in 1999, and helped the team reach the playoffs for the first time in franchise history, with a record of 20–12.

After the Sacramento Monarchs ended the Sparks' run in the first round of the 2004 WNBA Playoffs, Cooper took a job as an assistant coach under Jeff Bzdelik with the Denver Nuggets.

In May 2009, Cooper was named head coach of the University of Southern California's Women of Troy Basketball Team.

In 2019, Cooper was named the boys varsity coach at Chadwick School in the Palos Verdes Peninsula of Los Angeles County.