Gail Amundrud took up competitive swimming at the age of ten and made her international debut at the 1973 World Championships, where she finished fifth in the 4x100 metre medley relay alongside Wendy Cook-Hogg and the non-Olympians Patti Stenhouse and Mary Stewart. Her next stop was the 1974 Commonwealth Games, where she captured gold in the 4x100 metre freestyle relay (with Anne Jardin, Becky Smith, and Judy Wright), silver in the 100 metre freestyle, and bronze in the 200 metre version. In 1975 she earned bronze in the 4x100 m freestyle relay (with Jardin, Smith, and the non-Olympian Jill Quirk) at the World Championships and silver in the 4x100 m freestyle relay (with Jardin, Quirk, and the non-Olympian Janice Stenhouse) and the 200 m freestyle event at the Pan American Games. She was then selected to represent Canada at the 1976 Summer Olympics, where she won bronze in the 4x100 m freestyle relay, alongside Jardin, Smith, Barbara Clark, and Debbie Clarke. She also placed fifth in the 200 m freestyle and was eliminated in the semifinals of the 100 m version.
Amundrud entered Arizona State University in 1978 and was a member of their swim team through 1981, earning numerous accolades over her collegiate career, including recognition as the institution’s Female Athlete of the Year in 1979. She also continued to compete internationally for Canada, taking bronze in the 4x100 m freestyle relay at the 1978 World Championships (with Nancy Garapick, Wendy Quirk, and Susan Sloan) and gold in the same event at that year’s Commonwealth Games (alongside Wendy Quirk, Sloan, and Carol Klimpel). Her final major international tournament was the 1979 Pan American Games and she made the most of it, winning four medals: silver in the 4x100 m freestyle (with Klimpel, Jardin, and Wendy Quirk) and medley (alongside Garapick, Cheryl Gibson, and the non-Olympian Anne Gagnon) relays and bronze in the 100 and 200 m freestyle events. She was a medal hopeful for the 1980 Summer Olympics, but stayed at home after Canada joined the boycott of those Games, and retired from active competition upon her graduation from Arizona State. She has been inducted into the Sun Devil (Arizona State) Athletics, Ottawa Sports, and Swim BC Halls of Fame.