After the spring classics, Pidcock switched to mountain bike racing as part of his preparation for competing in the discipline at the 2020 Summer Olympics. In his first appearance in the elite category of the Mountain Bike World Cup in Albstadt, Pidcock moved forward from his starting position of 76th in the field to lead the race at the start of the third lap before eventually crossing the finish line in fifth. At the second round of the 2021 Mountain Bike World Cup in Nové Město in May, Pidcock took the win, being the only rider who could keep pace with Mathieu van der Poel for the first two laps, before attacking the Dutch rider on the third and crossing the finish line a minute ahead of Van der Poel. At the end of May Pidcock broke his collarbone in a training crash that prevented him from returning to the road in the Tour de Suisse the following month, however following surgery he was able to return to training on the road after just over a week. At the Olympics in July, Pidcock took the gold medal in the cross-country mountain bike competition, taking the lead midway through the race and crossing the finish line 20 seconds ahead of second placed Mathias Flückiger. This was the first ever Olympic medal for a British rider in mountain biking, and Pidcock also became the youngest rider to win an Olympic mountain bike title, being 79 days younger than Jenny Rissveds when she was crowned Olympic champion at the 2016 Summer Olympics.