[2] Anderson finished the 1998–99 season with the Guelph Storm of the Ontario Hockey League (OHL), where he served as a backup to Chris Madden.

In 2000–01, Anderson became the starter for the Storm, as he appeared in 59 games, earning a record of 30–19–9 with a 2.63 GAA along with a .918 save percentage to win the OHL Goaltender of the Year award.

In an interview with Sportsnet in 2011, Anderson admitted he added an extra s to his surname following a tournament in Sweden, in which he said was to serve as a memento to his time in the country.

Upon being drafted by the Calgary Flames in 1999, he was recognized in the team's official records as Craig Andersson, despite the fact it wasn't actually his legal surname.

Anderson was forced to abandon the practice of using the extra letter upon signing his first professional contract with the Chicago Blackhawks.

[4] The Chicago Blackhawks assigned Anderson to the Norfolk Admirals of the American Hockey League (AHL) for the 2001–02, where he served as a backup to Michael Leighton.

In his first NHL game on November 30, 2002, Anderson stopped all four shots he faced after replacing Jocelyn Thibault in the second period in a 4–1 loss to the Los Angeles Kings.

Anderson then started his first NHL game the next night, on December 1, 2002, against the Mighty Ducks of Anaheim, where he made 23 saves in a 3–2 loss.

Anderson set an NHL record for the most saves in a shutout, as he stopped all 53 shots he faced in a 1–0 win over the New York Islanders on March 2, 2008.

[5] Anderson joined the Colorado Avalanche for the 2009–10 season and won the starting job from Peter Budaj in training camp.

In his first season with the Avalanche, Anderson went 38–25–7 with a 2.64 GAA, .917 save percentage and seven shutouts, helping the team make a surprising run into the playoffs.

In his next start, Anderson recorded his first shutout with the team, stopping all 35 shots in a 3–0 win over the Vancouver Canucks on October 3, 2009.

Anderson became the fourth goaltender in team history to win 30 or more games, joining Patrick Roy, David Aebischer and Peter Budaj.

Four nights later, Anderson recorded his first ever post-season shutout, as he stopped all 51 shots fired at him, as Colorado won the game 1–0 in overtime.

With Colorado quickly falling out of the playoff race, and Anderson struggling with a 13–15–3 record and a 3.28 GAA, the club traded him to the Ottawa Senators for Brian Elliott on February 18, 2011.

[6] During the 2011–12 season, Anderson was among the league leaders for wins with 29 in 56 games before being sidelined in mid-February by a right hand injury sustained in a cooking accident.

In his first ten games of the season, he posted a record of 6–2–2 with a 1.49 GAA and .950 save percentage, earning consideration as an early Vezina Trophy favorite.

[12] On August 25, 2014, the Senators announced they had signed Anderson to a three-year, $12.6 million contract extension, starting in the 2015–16 season.

[16] During the 2017 Stanley Cup playoffs, Anderson backed the Senators to an appearance in the Eastern Conference Final, losing to the Pittsburgh Penguins in seven games.

Following the season, Anderson was the recipient of the 2016–17 Bill Masterton Memorial Trophy for perseverance, sportsmanship, and dedication to the sport of hockey.

[17] In June 2018, it was revealed that Anderson had quietly requested a trade from Ottawa, with his agent Justin Duberman being quoted as saying that his client "had expressed his desire to move on from the Senators.

"[18] By August, Anderson had seemingly changed his mind and hinted that some well-publicized discord within the Senators organization, which culminated in forward Mike Hoffman leaving the team after his girlfriend had been accused of harassing the family of All-Star defenseman Erik Karlsson, had been behind his earlier request to be moved.

Anderson made his first start as a Capital on February 21, stopping 26 of 29 shots and earning his first victory with the team as Washington defeated the New Jersey Devils 4–3.

He made 22 saves and allowed one goal as the Capitals defeated the Boston Bruins 3–2 in overtime in Game 1 of the 2021 Stanley Cup playoffs.

After missing time to care for his wife and children, Anderson played a key role in Ottawa's run to the 2017 conference finals.