Nelson had a career record of 339-251 as the Mavericks' head coach, and was instrumental in building some of the franchise's most successful teams, acquiring such players as Dirk Nowitzki, Josh Howard and Marquis Daniels as late 1st-round draft picks and unsigned rookie free agents, then watching them blossom into stars. He stepped down as coach of the Mavericks during the 2004-2005 season, turning the reins over to Avery Johnson (a former Mavericks guard). After the 2005 playoffs, his son Donnie, at the time the Assistant General Manager, was named General Manager.

He has also coached for the Milwaukee Bucks, Golden State Warriors and, briefly, with the New York Knicks. An innovator, Nelson is credited with, among other things, inventing the concept of the "Point Forward", a tactic which is frequently employed by teams at every level today.

In 1962, Don Nelson graduated from the University of Iowa as a two time All-American averaging 21.1 points and 10.5 rebounds a game. He was drafted 19th overall by the Chicago Zephyrs of the NBA. He played for the Zephyrs for two years until being sold to the Los Angeles Lakers in 1964. He was released the following year (1965) and signed by the Boston Celtics. Nelson completed his best NBA season averaging 10.2 points and 5.4 rebounds, and led the Celtics to NBA title as one of their role players. Nelson was coined as one of the "best sixth men" ever to play in the NBA. In 1976, Nelson began his career as an assistant coach for the Milwaukee Bucks, while still playing as a player for the team. He retired from playing after a 14 year tenure as a player. His number 19 was retired in the Boston Garden rafters in 1978, and still stands today at the Garden's replacement, TD Banknorth Garden.

Nelson took over the reins of General Manager and Coach of the Milwaukee Bucks in 1976 and began to show what would later become his signature style of wheeling and dealing players. He made his first trade of Swen Nater to the Buffalo Braves and turned the draft pick he received into Marques Johnson, who had a solid career with the Bucks. He earned NBA Coach of the Year honors in 1983 and 1985. It is in Milwaukee where he introduced the concept of the point forward. With a lineup consisting of Sidney Moncrief, Terry Cummings, Ricky Pierce and later on, Jack Sikma, Nelson's use of Paul Pressey to direct the offense led the Bucks to many Central Division championships and playoff berths. He would leave Milwaukee after ten seasons, seven with over 50 wins.

After a year's hiatus, Nelson then became Coach and Vice President of the Golden State Warriors, and was named NBA Coach of the Year a third time. He recruited tons of talent at Golden State with players such as Tim Hardaway, Latrell Sprewell, and Chris Webber. He left Golden State after disputes with Webber and a 14-31 start. He was invited to coach the Dream Team II at the 1994 World Championships in Toronto. He accepted and led them to the Gold Medal.

In 1995, Nelson would begin his stint with the Knicks, which lasted from that July until March of 1996. Nelson had many personal problems with the players, though, and led them to a lackluster 34-25 start. Nelson tried to convince management to trade Patrick Ewing in order to be in position to make an offer to rising free agent Shaquille O'Neal. He also favored a more up-tempo style of offense, sharply contrasting with the Knicks hard-nosed defensive style of play.

Nelson was named Head Coach and General Manager of the Dallas Mavericks in 1997, and led them to four consecutive 50 win seasons. The trio of Steve Nash, Michael Finley, and Dirk Nowitzki became the foundation for the dramatic turnaround. In Dallas, Nelson created an offensive powerhouse in which every player could score at any time. However, lacking interior defense - as the frontcourt with Raef LaFrentz, Shawn Bradley and Nowitzki was weak in the paint - they never reached the NBA Finals.

One notable result of Nelson's tenure at the helm of the Mavericks was the introduction of the somewhat controversial "Hack-a-Shaq" defense to the NBA.

On March 19, 2005, Nelson stepped down as Dallas' Head Coach, naming Avery Johnson as his successor. Nelson retained his job as Dallas' GM until after the season, when he named his son, Donnie Nelson, as his replacement.