He most recently coached the Sacramento Kings; previously in his career he has served as head coach of the Golden State Warriors and the Portland Trail Blazers.

Adelman began his basketball career as a collegiate star at Loyola Marymount University. In the 1968 NBA Draft, he was selected by the San Diego Rockets (now the Houston Rockets) in the 7th round. He played two seasons in San Diego before being taken by the expansion Trail Blazers in the 1970 expansion draft; he then played three seasons in Portland. He also played for the Chicago Bulls, New Orleans (now Utah) Jazz, and the Kansas City/Omaha (now Sacramento) Kings. He retired from playing basketball in 1975.

From 1977 through to 1983, Adelman coached at Chemeketa Community College in Salem, Oregon, after which he was hired by the Portland Trail Blazers (then coached by Jack Ramsay) as an assistant. When Ramsay was fired and replaced with Mike Schuler in 1986, Adelman was retained; when Schuler was in turn fired during the 1989 season (when poor team chemistry resulted in the team having a losing record), Adelman was promoted to interim coach. After leading the team into the playoffs that year (despite a 39�43 record), Adelman was given the coaching position on a full-time basis in the 1989 off-season.

The next three years were quite successful for Adelman and the Trail Blazers; the team went to the NBA Finals in 1990 and 1992 (losing to the Detroit Pistons and the Chicago Bulls in the finals); and went to the Western Conference finals (losing to the Los Angeles Lakers in 1991. Adelman spent two more years with the team, but was dismissed after the 1993�1994 season.

In 1995, Adelman was hired as the head coach of the Golden State Warriors. He was unable to duplicate his success in Portland, and was fired after only two years with the team.

After a year's absence from the sidelines; Adelman was hired by the Sacramento Kings in 1998. Under Adelman's guidance, the Kings were one of the more successful Western Conference teams, qualifying for the playoffs every year since Adelman joined the franchise. However, the Kings never advanced to the NBA finals during Adelman's tenure.

In 2005, Adelman's name was mentioned as a possibility to replace Maurice Cheeks in Portland (where he still has family connections and still maintains a home). However, management of the Kings reportedly turned down a request from the Trail Blazers to interview Adelman.

In 2006, Adelman (in the final year of his contract) led the Kings to the 2006 NBA Playoffs. Despite the team struggling early, the Kings rebounded and qualified for the playoffs as the #8 seed, due in large part to the addition of Ron Artest via trade with the Indiana Pacers. Although competitive, they were defeated 4-2 by the defending champion San Antonio Spurs. Adelman's contract with the Kings expired at the end of the 2005�2006 season. On May 9, it was reported by the Sacramento Bee that his contract would not be renewed.

Adelman is widely regarded around the league as a "player's coach", and is considered one of the more capable coaches in the NBA. However, he is sometimes criticized for being too hands-off; some NBA observers have suggested that Adelman's teams are not as fundamentally sound as their opponents. Adelman's defenders counter that his teams have often over-achieved: advancing deep into the playoffs without the benefit of a superstar such as a Michael Jordan or Shaquille O'Neal.

Adelman has a long association with Kings' general manager (and fellow ex-Trail Blazer) Geoff Petrie.