Bilodeau played hockey as a youngster, but his family encouraged him to switch to skiing because it was a sport that could be enjoyed by the whole family, including Alex’s older brother Frédéric, who has cerebral palsy and is unable to skate. Though not initially fond of the sport, Bilodeau was a natural jumper and excelled at freestyle skiing, and began his competitive career in his early teens. Bilodeau initially competed in both aerials and moguls, but soon focused on the latter and joined the national team's development program in 2004. His background in aerials strengthened his skills as a mogul skier, and at just 14 years old he became the youngest athlete to perform a triple jump in competition.
Bilodeau started his competitive years strongly, becoming the first freestyle mogul skier to perform a double twisting flip in competition, at the 2005 Fernie Nor-Am, and the youngest man in International Ski Federation (FIS) history to win a gold at a World Cup event, at the 2006 Ski Mont Gabriel. Bilodeau also qualified for the Torino Olympic Games in 2006, where he placed 11th. For his accomplishments the FIS named Bilodeau 2005–06 Rookie of the Year for men's moguls.
Though his career started strong, problems with concentration during competition soon forced his stats down, and Bilodeau looked to other training methods such as biofeedback to regain his focus. The training helped, and his 2008–09 season ended well. In 2009, Bilodeau and teammates Vincent Marquis and Pierre-Alexandre Rousseau had an unprecedented Canadian podium sweep at the Ski Mont Gabriel World Cup, winning silver, gold and bronze respectively. In all, Bilodeau garnered five World Cup golds and three silvers in moguls and dual moguls, and a world championship title in the dual moguls leading up to the Vancouver 2010 Olympics. The season also yielded three significant international titles for Bilodeau: 2009 FIS Overall Champion, 2009 FIS World Cup Mogul Champion and 2009 Dual Mogul World Champion.
2010 Olympic Winter Games
Coming into the 2010 Winter Olympic Games, Bilodeau was ranked fourth in the world standings. Though conditions at Vancouver's Cypress Mountain were challenging and slushy, Bilodeau executed a perfect back-flip and flawless run through the moguls, scoring 26.75 points and unseating the reigning Olympic champion, ex-patriate Canadian Dale Begg-Smith, who competed for Australia. Begg-Smith took silver with his score of 26.58 points, and US skier Bryon Wilson won bronze with 26.08 points. It was Canada's first Olympic gold in moguls since Jean-Luc Brassard's win in 1994. In addition to Brassard, Bilodeau cites his brother Frédéric as one of his greatest inspirations.
In the four years between the 2010 and 2014 Olympic Winter Games, Bilodeau won two world championships in dual moguls — in 2011 in Deer Valley, Utah, and in 2013 in Voss, Norway. He also had continued success in moguls, winning two silver medals at the world championships, and was second on the World Cup circuit in 2011 and 2013.
Heading into the 2014 calendar year, Bilodeau was not favoured to defend his Olympic gold medal at the 2014 Olympic Winter Games in Sochi. The world’s top mogulist at the time was another skier from Québec, Mikaël Kingsbury, who was the reigning world champion, World Cup champion, and winner of the first three World Cup competitions of the 2013–14 season. At a World Cup in Calgary on 4 January 2014, Bilodeau was very disappointed that he finished 1.74 points back of Kingsbury and thought he deserved a better score. Kingsbury would best Bilodeau again five days later in Deer Valley, Utah.
The turning point in Bilodeau’s season came on 11 January 2014, when he beat Kingsbury by a narrow seven one-hundredths of a point to win another World Cup event in Deer Valley, Utah. Bilodeau believed the reason for this success was his ability to execute techniques with a high degree of difficulty, even in qualification (which does not count in total score, but determines the seeding for the final round). Bilodeau would go on to win two more World Cups in Lake Placid, New York, and Val St. Come, Québec, before attempting to defend his Olympic gold medal.
2014 Olympic Winter Games
At the 2014 Olympic Winter Games in Sochi, Bilodeau won his second consecutive gold medal, with Kingsbury winning silver. However, winning Olympic gold would not be easy. In the first final where the field was cut from 20 to 12 athletes, Bilodeau finished in eighth place after a stumble. In the second final, which limited the field from 12 to 6, he was behind Kingsbury and Canadian Marc-Antoine Gagnon.
Bilodeau saved his best performance for last. In the third final, he executed a back double full and off-axis 1080 to perfection, posting a score of 26.31 points. The 2014 Olympic Winter Games was an excellent moguls competition for Canadian men. Not only did Bilodeau and Kingsbury finish first and second, but two other Canadians finished in the top ten, with Gagnon fourth and Philippe Marquis ninth.
Bilodeau formally retired from freestyle skiing in October 2014. He received a Bachelor of Business Administration from Concordia University in 2016 and a graduate diploma in accounting from HEC Montréal in 2017. Bilodeau has been a brand ambassador for a number of companies, including KPMG Canada and Nike.
Bilodeau is Honourary Chair of the Alexandre Bilodeau Fund for Adapted Sports at the MAB-Mackay Rehabilitation Centre in Montréal. The fund supports adapted sports programs for children with motor, hearing, vision and language impairments, including hydrotherapy, hippotherapy (adapted horseback riding), community sports and training for competitive events. It is a cause close to Bilodeau’s heart. “Because my older brother Frédéric has cerebral palsy, I’ve always been inspired by children with physical impairments — they’ve encouraged me to become the athlete I am today.” He has been involved with the Cerebral Palsy Association in Alberta, the Association de paralysie cérébrale du Québec and the Canadian Association of Paediatric Health Centres for Cerebral Palsy Research. Bilodeau was also president of the organizing committee for the 2016 Quebec Games in Montréal.