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 1988-89 season, 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 respectively) and went to the Western Conference finals in 1991 (losing to the Los Angeles Lakers). 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 most successful Western Conference teams, qualifying for the playoffs during every year of his Sacramento career.
During the Kings' 2000 playoff run, they met Phil Jackson's Los Angeles Lakers. Adelman questioned Jackson's motivational techniques when it was learned that Jackson compared Adelman to Adolf Hitler.
In 2002, the Kings made a serious run for the NBA Finals. After clinching the first seed in the competitive Western Conference, the Kings blazed through the opening two rounds but lost to the Lakers in a hard fought seven-game series.
In 2006, Adelman (in the final year of his contract) led the Kings to the playoffs. Despite the team struggling early in the regular season, the Kings rebounded and qualified for the playoffs as the #8 seed. 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. The Kings have yet to reach the playoffs since.
The Houston Rockets brought in Rick Adelman as their new head coach, five days after the dismissal of Jeff Van Gundy, on May 18, 2007. Van Gundy had taken the Rockets to three playoff appearances in four years with no series wins. In his first season as head coach, Adelman guided the Rockets to a 22-game winning streak from January through March 2008, the third-longest winning streak in NBA history.
In the 2009 season, the Rockets finished 5th in the West with a 53–29 record. They entered the playoffs without their star shooting guard, Tracy McGrady, due to an injury. Despite this loss, the Rockets defeated the Portland Trail Blazers in six games to advance to the Western Conference Semifinals for the first time since 1997. However, they lost to the Los Angeles Lakers, but surprised many people and proved their resilience by taking the series to seven games even though their star center, Yao Ming, had a season-ending injury in Game 3 of that series.
Adelman won his 800th career game, 13th among coaches in NBA history, on March 24, 2008 against his old team the Sacramento Kings.
On April 18, 2011, Houston Chronicle reported that the Houston Rockets would not give Adelman a new contract, and would part ways after 4 seasons.
On April 6, 2013, Adelman won his 1000th career game with a victory over the Detroit Pistons, becoming just the 8th coach in NBA history ever to do so. Adelman's victory came in front of a home crowd of 15,311, including his wife, Mary Kay, whom he promptly joined after the game to celebrate the occasion. The win came 24 years, 1 month, and 11 days after his first win with the Trail Blazers (February 26, 1989).