During the following season, 2012–13, Gibson was selected to represent the United States at the 2013 World Junior Ice Hockey Championships. He was the team's primary goaltender throughout the championship, registering a .955 save percentage and a 1.36 goals against average (GAA) in seven games for the eventual gold medal winners.[5] His save percentage led all goaltenders in the tournament and he was named as the tournament's best goaltender.[6][7] He was also named to the tournament All-Star Team, as well as named the tournament's most valuable player.[8][9]
Gibson made his professional debut with the Norfolk Admirals, the American Hockey League (AHL) affiliate of the Anaheim Ducks, on April 19, 2013, playing 40 minutes in relief.[12]
On April 7, 2014, aged 20 years and 297 days, Gibson made his first NHL start for the Ducks following an injury to goaltender Frederik Andersen. Making 18 saves for a shutout, Gibson earned his first NHL win, a 3–0 victory over the Vancouver Canucks.[13] In doing so, Gibson became the youngest NHL goaltender to record a shutout in his NHL debut since the Buffalo Sabres' Daren Puppa (20 years, 223 days) performed the feat in the 1985–86 season.[14] Gibson made his Stanley Cup playoff debut with the Ducks in Game 4 of the Western Conference Semifinal against the Los Angeles Kings. He registered a shutout on 28 shots and was named first star of the game on May 10, 2014.[15]Jonas Hiller, whom Gibson started over, was the last goaltender prior to Gibson to record a shutout in his Stanley Cup playoff debut. The Ducks would win Game 5 at home 4–3 but would lose Games 6 and 7 by scores of 2–1 and 6–2, respectively, with Gibson being pulled in Game 7 after allowing 4 goals on 18 shots.[16]
With the departure of Jonas Hiller via free agency, the Ducks announced that both Frederik Andersen and John Gibson would compete for the number one starting job for the 2014–15 NHL season.[17] Gibson seemed to have performed well enough in the preseason to start opening night against the Pittsburgh Penguins, his hometown team, in which Gibson stopped 33 of 39 shots en route to a 6–4 loss.[18] With Andersen starting off the season strong, Gibson was sent to Norfolk for a weekend to gain some playing time. Afterwards, he was recalled by the Ducks. Upon his return Gibson won his next two starts and lost one, which included a shutout of the Chicago Blackhawks. Gibson then injured his groin while warming up before a game against the Colorado Avalanche. He was estimated to miss six to eight weeks, thus giving Andersen total control of the number one job and the Ducks signed Ilya Bryzgalov as a backup to Andersen in Gibson's absence. After coming off injured reserve, Gibson spent time off with Norfolk.[19] When Andersen went down with an injury, Gibson was recalled.[20] When Andersen returned, the two goalies would rotate in and out of the crease with Gibson at one point being considered as the starter down the stretch with Andersen struggling a bit. Overall, Gibson would post up a record of 13–8 with a 2.60 goals against average and a save percentage of .914%. He did not see a single minute of play during the Ducks postseason run, missing the entire first round due to an upper-body injury.[21] The Ducks went all the way to the Western Conference Finals but fell to the eventual Stanley Cup Champions, Chicago Blackhawks in seven games.[22]
With the off-season acquisition of Anton Khudobin, rumors sparked of Gibson being traded elsewhere, which was promptly put down by Ducks general manager Bob Murray. On September 21, the Ducks announced that they signed Gibson to a three-year contract extension, worth reportedly $6.9 million. He also began the 2015–16 season with the new AHL affiliate, the San Diego Gulls. When Andersen had the flu, Gibson was recalled on November 24 and started when the Calgary Flames met the Ducks in which the Ducks won 5–3. Gibson started for the next nine games posting a 4–4–1 record. He was named the NHL's Rookie of the Month in December 2016.[23] On January 6, 2016, it was announced that Gibson was selected to his first All-Star Game.[24] Gibson started the first round playoff series with the Nashville Predators, but lost the first two games. Andersen replaced him, but it was not enough and Anaheim was eliminated.[25] Andersen and Gibson combined to win the 2016 William M. Jennings Trophy for the lowest goals scored against.[26] Gibson was also named to the NHL's 2016 All-Rookie Team.[27] However, that offseason, the Ducks traded Andersen to the Toronto Maple Leafs and made Gibson the undisputed starter.[25] The Ducks made the playoffs at the end of the 2016–17 season, however, they were swept by the San Jose Sharks in the first round.[28]
On August 4, 2018, the Ducks re-signed Gibson to an eight-year, $51.2 million contract extension worth $6.4 million annually.[29] He made his second All-Star appearance at the 2019 NHL All-Star Game.[30] Gibson appeared in 46 games (45 starts) going 17–19–8 before being injured in a collision with teammate Jaycob Megna during a 4–0 loss to the Ottawa Senators on February 7, 2019. On February 13, 2019, Gibson was placed on injured reserve by the Ducks, due to head, back, and neck injuries obtained from a collision Megna.[31] He returned to the lineup on March 1 in a 3–0 loss to the Vegas Golden Knights, making 32 saves on 34 shots.[32] The 2019–20 season marked Gibson's fifth straight 20-win season.[33] During the 2020–21 season marked a downturn in Gibson's performance for the first time, with only a .904 save percentage and a 3.00 goals against average.[34]
Gibson began the 2021–22 season as the team's starter, backed up by Anthony Stolarz and Lukáš Dostál. He began the season demanding a turnaround in the team's play.[28] He was named to the 2022 NHL All-Star Game representing the Ducks for the third time.[35] The Ducks were in the playoff race until the All-Star Game, which they followed up with a losing skid and never got back in. They ended up missing the playoffs.[36] This was reflected in Gibson's play, which saw him struggle following the All-Star Game.[37] During the 2022–23 season, Gibson again played on a struggling Ducks team, leading or among the leaders in saves during the majority of the season. On March 10, 2023, Gibson set a new franchise record for career saves with the team, surpassing Guy Hebert's mark of 11,813 in a 3–1 victory over the Calgary Flames.[38] The Ducks failed to make the postseason for the fifth straight year.[39]