He returned to Team Penske for the 2005 season. At Phoenix in the season's second race, Hornish started in second place and won after leading for 25 laps. During practice for the Indianapolis 500, he drove over a piece of debris after Paul Dana's second-turn crash and flipped over. Two days later Hornish qualified in second place, crashing out after leading for a race-high 77 laps and finishing 23rd. At the Milwaukee Mile he qualified for the pole position and led for 123 of 225 laps, passing Dario Franchitti with nine laps left for his second win of the season. Hornish finished third in the championship standings, with 512 points.