He was an outstanding local point guard at St. Pius X HS in Downey before playing at Loyola University of LA (now Loyola-Marymount) from 1965-68. He was the WCC Player of the Year in 1968 and twice All-Conference. He was inducted into the LMU HOF in 1986. He was a 7th round draft pick of the San Diego Rockets and had a seven-year NBA playing career, competing in 462 games before going into coaching. He spent 37 years in pro basketball, including the last 25 as a NBA head coach. The 6-1, 175-pound Adelman was the Portland Trailblazer Asst. Coach before becoming head coach in 1989. He went to two NBA finals and one conference finals in five years.

He then coached the Golden State Warriors, before moving for a successful run with the Sacramento Kings, going to the playoffs every year in the best period in their franchise history. He then coached the Houston Rockets where he won his 800th career game, before finishing his career with Minnesota. He won his 1000th game on April 6, 2013. He retired after the following season. He won 1042 games in his career to rank in the top ten all-time in NBA victories and was a three-time All-Star game head coach. He was inducted into the Naismith Hall of Fame in 2021.