Price made his highly anticipated Canadiens debut on October 10, 2007, against the Pittsburgh Penguins and recorded 26 saves in a 3–2 win. After the first month of the season, he was awarded the Canadiens’ Molson Cup for October, given to the player with the most first-star selections. Although reassigned to the Hamilton Bulldogs midway through the season in January, he was called back up shortly over a month later. With the trading of starting goaltender Cristobal Huet to the Washington Capitals before the trading deadline, Price assumed the starting role for the Canadiens. He was subsequently named the NHL Rookie of the Month for March and the NHL First Star of the Week (ending April 6, 2008) as the Canadiens finished first overall in the Eastern Conference and earned their first division title since 1991–92. Price completed the regular season leading all rookie goaltenders in wins (24), save percentage (.920) and shutouts (3). He was named to the NHL All-Rookie Team in recognition for his accomplishments in his first year in the NHL.

Entering the playoffs against the Boston Bruins, Price recorded a 1–0 win on April 15, 2008, becoming the first Canadiens rookie to post a playoff shutout since Patrick Roy in 1986. He would go on to record another shutout in game seven to eliminate Boston. Montreal lost in the second round to the Philadelphia Flyers with Price losing 3 of the last 4 games.

After a strong start to the 2008–09 season, in which he earned a second Molson Cup in November, Price injured his ankle on December 30, 2008. Forced out of action for nearly a month, during which he was voted in as a starting goalie for the 2009 NHL All-Star Game in Montreal (along with teammates Alexei Kovalev, Andrei Markov and Mike Komisarek) he made his return to action on January 20, 2009, after backup Jaroslav Halák was pulled in a 4–2 loss to the Atlanta Thrashers. Going into the 2009 playoffs as the eighth and final seed, the Canadiens played the Boston Bruins in the opening round for the second consecutive season. They were swept in four games, with the Bruins scoring at least four times in each game. In the final game at the Bell Centre in Montreal, Price surrendered four goals in two periods. After stopping a weak dump-in, the crowd cheered sarcastically and Price responded by putting his arms up in the air, similar to Patrick Roy’s gesture on December 2, 1995, in a game after which Roy requested a trade from the Canadiens.

Price struggled throughout the 2009–10 season, winning only 13 games and losing the starting job to Halak as the Canadiens entered the playoffs as the eighth and final seed. Although the Canadiens made a surprise run to the Eastern Conference final, upsetting both the Washington Capitals and Pittsburgh Penguins along the way, Price appeared in only four games, losing one and getting no decision in each of the others, only coming off the bench when the game was out of hand. The highlight of the season for Price was stopping 37 of 38 shots in a 5–1 win over the Boston Bruins in the Canadiens 100 year anniversary game on December 4, 2009, and the low point was surrendering four goals in his only start of the playoffs. In the summer of 2010, both Price and Halák became restricted free agents and a goaltending debate emerged in Montreal over who would remain with the team – the playoff hero Halák or the younger Price. After weeks of media speculation, the Canadiens chose Price, trading Halák to the St. Louis Blues and re-signing Price to a two-year, $5.5 million contract to return to his role as starting goaltender.

Price, who is of Ulkatcho First Nation descent through his mother, was named as an honorary co-chair at the 2010 National Aboriginal Hockey Championships that were held in Ottawa, Ontario, in May 2010. Price is of the Nuxalk and Southern Carrier Aboriginal heritage. Price is very proud to be of the descent from the line of chiefs and leaders including his mother, Lynda.

The 2010–11 pre-season was a tough start for Price. During the 2010–11 regular season, however, Price played in 72 games recording new career highs including 38 wins, eight shutouts a 2.35 GAA and a .923 save percentage, and was selected to play in the 2011 NHL All-Star Game. This play from Price allowed the Canadiens to enter the 2011 Stanley Cup playoffs. This strong play continued for Price in the playoffs posting a .935 save percentage. It was not enough, however, to lead the Canadiens to victory, as they ultimately fell in seven games in the first round to the Boston Bruins. On October 26, 2011, Price earned his 100th win in his NHL career in his 214th game. A few months later, he participated to his third All-Star Game. The 2011–12 season, however, did not go well for the Canadiens, and they missed the playoffs for the first time since the 2006–07 season. Price missed the last 4 games of the season due to a concussion.

On July 2, 2012, Price re-signed with the Canadiens on a six-year contract worth US$39 million.

On January 7, 2014, Price was named to the 2014 Canadian Olympic Hockey Team along with goaltenders Mike Smith of the Phoenix Coyotes and Roberto Luongo of the Florida Panthers. Price, along with close friend and teammate P. K. Subban, became the first Montreal Canadiens players to be selected for Team Canada since Mark Recchi in the 1998 Nagano Olympics. Soon after arriving in Sochi, it was announced that Price would start in Canada’s first game of the tournament against Norway. Price had a strong debut, stopping 18 of 19 shots against Norway in a 3–1 Canadian win. Price’s strong play continued, allowing only a single goal in a 2–1 victory against Finland in the round-robin tournament. In Canada’s quarter-final game, Price backstopped Canada over Latvia 2–1. On February 21, 2014, Price played a pivotal role in a 1–0 victory against Team USA in the semifinals. Price stopped all 31 shots and shutout Team USA, powering Team Canada into the gold medal game against Sweden. In his second consecutive shutout of the Olympics, Price made 24 saves in a 3–0 victory and won his first gold medal as an Olympian. Price ended the tournament undefeated in five games with a 0.59 GAA and .971 save percentage, and was named the tournament’s best goaltender by the International Ice Hockey Federation (IIHF).

In 2015, Price teamed up with CCM to donate $10,000 worth of equipment to a minor hockey league in Williams Lake, B.C. Additionally, Price funds a breakfast program at his old school in Anahim Lake, B.C.

Price met his wife, Angela (née. Webber), while playing with the Tri-City Americans. In an interview, Angela said that the couple were set up on a blind date by her friend, who was dating Carey’s roommate at the time. They reside in Kelowna, British Columbia, during the off-season. They were married August 24, 2013, in Benton City, Washington, near Angela’s hometown of Kennewick. The next day, Price flew to Calgary for Hockey Canada’s Olympic orientation camp for the 2014 Winter Olympics. On October 21, 2015, Angela Price confirmed on her blog that they were expecting their first child due the following spring. In 2016, Angela gave birth to the couple’s first daughter. In December 2018, Angela gave birth to their second daughter. In June 2020, Angela announced they were expecting their third child due in the fall.

Early in the 2015–16 season, Price suffered a knee injury. At the time of injury, he was expected to return after six weeks. However, on April 6, 2016, the Canadiens announced that Price would not return for the 2015–16 season. The extent of Price’s injury was revealed to be a medial collateral ligament injury (MCL sprain).

On July 2, 2017, it was announced that Price signed an eight-year contract extension with an annual cap hit of US$10.5 million totalling to US$84 million for the entire contract. His new contract will run through the 2025–26 season. This will make Price the highest paid goaltender in the 2018–2019 NHL season, surpassing goaltender Henrik Lundqvist.

After a dismal month at the start of the 2017–18 NHL season Price was out for the count with a minor lower body injury, leaving goalies Al Montoya and Charlie Lindgren to take his place. On February 22, 2018, Price was rule out indefinitely after sustaining a concussion in a game against the Philadelphia Flyers. On March 19, 2018, Price returned from his concussion and dressed for the first time in 13 games for a game against the Florida Panthers. Despite his injuries, Price made in his 557th career NHL start for the Canadiens on April 3, 2018, surpassing the previous franchise record holder Jacques Plante.

On October 27, 2018, after a 3–0 win over the Boston Bruins, Price surpassed Patrick Roy for second place in Montreal Canadiens franchise career wins with his 290th career victory. Price was named to the 2019 National Hockey League All-Star Game, his sixth All-Star nomination, but he chose to defer due to a lower-body injury.

On March 12, 2019, after a 3–1 victory over the Detroit Red Wings, Price surpassed Jacques Plante for first place in Montreal Canadiens franchise career wins with his 315th career victory.

During the 2019 NHL Awards, Price, together with model Camille Kostek, presented Canadien hockey fan Anderson Whitehead the Feel Good Moment Award. Whitehead’s mother always wanted her son to meet the goalie, but wasn’t able to arrange it before she died last November at age 44 from cancer.