Millar fractured his collarbone in a crash in the 2012 E3 Harelbeke one-day race in Belgium on 23 March. He returned to competition at the Tour of Bavaria and the Critérium du Dauphiné, where his best result was a 9th place on stage 4. Despite his injuries earlier in the season, Millar was selected to ride his 11th Tour de France. He won stage 12 by escaping with four other riders, arriving from the finish line in Annonay-Davézieux with more than ten minutes of an advantage over the bunch. He took the win after much cat-and-mouse-play with Jean-Christophe Péraud of . He was the fourth British rider to win a stage in a tour, as Bradley Wiggins became the second British rider to win the event (Nicole Cooke won the women's Tour in 2006). Millar was selected to race on the British Road Race Team for the London Olympics. He reprised his role of team captain from the 2011 World Championships, again aiming to steer Mark Cavendish to victory. Millar and GB teammates Bradley Wiggins, Ian Stannard and Chris Froome were forced to set the tempo for the majority of the race, with little help from the other nations, and were eventually unable to reel back a thirty-man breakaway that had gone clear on the final climb of the Box Hill circuit, leaving Cavendish to come in forty seconds behind the winner, Alexander Vinokourov.