Félix Auger-Aliassime began playing tennis under the tutelage of his father, Sam Aliassime, at the age of five, and then became a member of the Académie de Tennis Hérisset-Bordeleau in Quebec City. In 2012, he won the Open Super 12 Auray. In 2014, he became a member of Tennis Canada’s National Training Centre in Montreal.

2015 was a breakout year for the junior player, with Auger-Aliassime winning his first junior singles title in Querétaro and then earning his second title a week later at Zapopan. At the 2015 US Open, his first junior Grand Slam event, Auger-Aliassime won the doubles title with Denis Shapovalov. The duo also won the first Junior Davis Cup title for Canada with the assistance of Benjamin Sigouin. At the 2015 Challenger Banque Nationale de Drummondville, Auger-Aliassime became the youngest player to qualify for an ATP Challenger main draw. Although he had to withdraw from the tournament due to an injury, he made history as the first player born in the 2000s to have an ATP ranking. He continued to set records in 2015 at the Challenger Banque Nationale de Granby where, after being defeated in the quarterfinals by Japanese player Yoshihito Nishioka, he became the youngest player to break the top 800 in the ATP rankings at No. 749.

In 2016, Auger-Aliassime won the boys singles title at the US Open and won his first professional title at Birmingham, Alabama. His first professional doubles victory came soon after at Niceville, where he competed alongside American Patrick Kypson.

Auger-Aliassime turned professional in 2017 and made history once more by becoming the first 16-year-old to win a Challenger singles title since Bernard Tomic in 2009 at the Open de Lyon. At the Copa Sevilla, Auger-Aliassime won his second ATP Challenger title after defeating former world number 56 Íñigo Cervantes and made more history by becoming the youngest player to break the top 200 since Rafael Nadal in 2002.

Auger-Aliassime’s first ATP Masters 1000 main draw came in 2018, when he qualified for Indian Wells. Although he lost in the second round, his first-round victory against fellow Canadian Vasek Pospisil marked his first tour-level match. He also became the youngest player to successfully defend an ATP Challenger title at Lyon, where he defeated French player Johan Tatlot in the finals.

2019 marked Auger-Aliassime’s first appearance in a Grand Slam tournament at the professional level when he played at Wimbledon. He lost in the third round to French player Ugo Humbert and also became the youngest ATP 500 finalist at the 2019 Rio de Janeiro tournament as well as the youngest semi-finalist at the 2019 Miami tournament. In 2021, he reached the quarterfinals at Wimbledon and the penultimate semi-final round at the US Open.

His first professional doubles title came in 2020 at the ATP Paris Masters alongside his partner, Hubert Hurkacz. Currently, Auger-Aliassime has two coaches—Frédéric Fontang (2016 to present) and Rafael Nadal’s uncle and former coach Toni Nadal (2021 to present). Auger-Aliassime received the 2021 US Open Sportsmanship Award. In January 2022 he achieved a No. 9 ranking after helping Canada win the 2022 ATP Cup title. One month later, Auger-Aliassime achieved his first ATP Tour singles title, winning the ABN Amro World Tennis Tournament in Rotterdamn over Stefanos Tsitsipas, 6-4, 6-2.

Felix was a key player on the Team World for the 2022 Laver Cup. He also was instrumental in helping Canada win their first Davis Cup in 2022. He reached his career high ranking of World No. 6 in November of 2022.  After a slow start to 2023, Felix was able to defend his title at the 2023 Swiss Indoors, despite entering the tournament seeded sixth.