The son of Georg Grünenfelder, an alpine skier at the 1964 Winter Olympics, Andi Grünenfelder first competed in cross-country skiing for Switzerland in 1982 and placed 20th in that year’s 15 km freestyle event. He first appeared at the Winter Olympics in 1984, with a best individual finish of sixth in the 50 km, and was fifth in the 4x10 km relay alongside Joos Ambühl, Giachem Guidon, and Konrad Hallenbarter. He continued competing for four years, but never won a major international medal or had a World Cup podium finish until the 1988 Winter Olympics, where he won a surprising bronze medal in the 50 km. He also narrowly missed a medal in the 4x10 km relay with Guidon, Jürg Capol, and Jeremias Wigger, came in 35th in the 15 km classical, and failed to finish the 30 km classical. Grünenfelder, formerly a physics and chemistry student at the University of Zürich, retired after the Games and returned to his studies. He eventually became a sports physician and was appointed chief at the Gut Klinik in St. Moritz.