[2] He attended the University of Southern California in Los Angeles and played college basketball for the Trojans at guard.

[3] After three seasons in Boston, including a championship in 1974,[4] the Celtics traded Westphal and two second round draft picks to the Phoenix Suns for Charlie Scott.

[10][11][12][13] Notably, Westphal exploited a loophole within NBA rules that effectively allowed the Suns to cede a point to get the ball at half-court with two seconds remaining at the end of the second overtime; the Suns tied the game thanks to the loophole.

[22] After missing most of the 1981–82 season, Westphal signed with the New York Knicks in late February 1982 after Seattle declined to match the offer.

[23][24][25] He was named the NBA Comeback Player of the Year in 1982–83, when he averaged 10 points and 5.5 assists and helped the Knicks qualify for the playoffs.

[31] Westphal's coaching career started in 1985 at Southwestern Baptist Bible College (now Arizona Christian University), located in Phoenix.

[32][34] With players such as Kevin Johnson, Dan Majerle, rookie Richard Dumas, Charles Barkley, and Danny Ainge, the Suns made it to the NBA Finals in Westphal's first season as a coach, but lost to the Chicago Bulls in six games.

In his first season, Westphal led the Waves to a 22–9 record and tied the nationally ranked Gonzaga Bulldogs for the WCC title.

The team received an at-large berth to the NCAA tournament, but lost 83–74 to Wake Forest in the first round, played at ARCO Arena in Sacramento.

[39] When Johnson was replaced by Rick Carlisle, Westphal left coaching to become executive vice-president of basketball operations (under Donnie Nelson) for the Mavericks in October 2008.

[34][42] For the 2014–15 season, Westphal was hired by the Brooklyn Nets as an assistant to new head coach Lionel Hollins.

[47][48] In August 2020, ESPN reported that he was diagnosed with brain cancer[49] which he succumbed to in Scottsdale, Arizona on January 2, 2021, at age 70.