Born in Toronto, Ontario, after attending North Toronto Collegiate Institute, Neilson's coaching career began as a university student at McMaster University in Hamilton, Ontario, and continued upon graduation with a degree in Physical Education in both hockey and baseball.
Neilson was head coach in the NHL for:
In 1979, Neilson was actually fired as head coach of the Maple Leafs by then-owner Harold Ballard. There was outrage throughout the players, media, and general public. Ballard then relented. Ballard wanted Neilson to enter the next game with a paper bag over his head (to be "the mystery coach") but Neilson refused and coached the next game as nothing had happened.
He was initially an assistant coach with Vancouver, but he took over as Head Coach after Harry Neale was suspended for taking part in an altercation with fans during a brawl in Quebec. When the team went unbeaten in the next seven games, he was given the job permanently. It was in his new capacity that Neilson led the team on its Cinderella run to the Stanley Cup finals (see below).
His tenure with the New York Rangers was also successful; the highlight was coaching the team to the Presidents' Trophy as the first place team in the league in 1992.
With Philadelphia, he led the team to first place in the Eastern Conference in 2000, a position that the team would retain for the rest of the regular season. With the Flyers leading in the conference standings by the midseason All-Star Game, Neilson earned the honour of being head coach of the Eastern Conference All-Stars. Previously, he had coached the Campbell Conference All-Stars at the 1983 All-Star Game.
Neilson was then hired as an assistant coach of the Senators. During the 2002–2003 season, Head Coach Jacques Martin stepped away from the bench for 2 games, allowing Neilson to take the reins and become the ninth man to coach 1000 games. It was also the most successful season in Senators' history up to that point, as they won the Presidents' Trophy as the first place team in the league, and made it all the way to the Eastern Conference Finals. As it was well known that Neilson's cancer was terminal when the Senators were eliminated in a tough seven game series, several players expressed their sadness at not being able to win the Stanley Cup for Neilson before he died.
Neilson's overall regular season record was 460 wins, 381 losses, and 159 ties.
Among his most well-known innovations was the use of videotape to analyze other teams, leading to the nickname "Captain Video". He was also the first to use microphone headsets to communicate with his assistant coaches.
Neilson was well known for closely reading the rule book looking for loopholes. During one particular game in the OHL his team was up one goal, but was down two men in a five on three situation for the last minute of the game. Realizing that more penalties could not be called under the existing rules, Neilson put too many men on the ice every ten seconds. The referees stopped the play and a faceoff was held relieving pressure on the defence. After this display the rule was changed so that a call for too many men on the ice in a 5 on 3 situation now leads to a penalty shot.
Neilson also discovered that if he put a defenceman in net instead of a goalie during a penalty shot, the defenceman could rush the attacker and cut down the latter's angle of shot, greatly reducing the chances of a goal. Today the rule states that a team must use a goalie in net for a penalty shot.
One game during a time-out, Neilson told his goaltender, “...when we pull you, just leave your goal stick lying in the crease.” When the other team gained possession, they sent the puck the length of the ice toward the open net, only to deflect wide when it hit the goal stick lying in the crease. The rule was changed the next season.
Neilson also broke the rules, in a sense, when he didn't like what was going on on the ice. As the Canucks coach during a 1982 playoff game against the Chicago Blackhawks, he felt his team was unfairly penalized on several occasions during the third period. He took a white trainer's towel and held it on a hockey stick, as if to wave a white flag. Three other Canucks players did the same thing, and all were ejected from the game. By doing this, Neilson inadvertently started an NHL tradition. Canucks fans waved white towels by the thousands at the next game, a playoff tradition that continues to this day and that is widely copied by other hockey teams and by other sports as well.
In 1999, Neilson was diagnosed with bone cancer, which spread to become skin cancer in 2001. He died on June 21, 2003, only five days after his 69th birthday, and the funeral was held in Northview Pentecostal Church in Peterborough.
Shortly after his death, the Ottawa Senators Foundation announced plans to build Roger's House/La maison de Roger, a pediatric palliative care facility built in his memory on the grounds of the Children's Hospital of Eastern Ontario in Ottawa. The building was opened on April 21, 2006, by the Premier of Ontario, Dalton McGuinty.
In September, 2004, a new elementary school in Peterborough named Roger Neilson Public School opened. The name was chosen because of Roger's commitment to teaching and that Roger exemplified the qualities of the Character Education program of the Kawartha Pine Ridge District School Board.