For 2005, Kanaan returned with Andretti Green Racing in the No. 11 7-Eleven-sponsored Dallara IR05-Ilmor-Honda Indy V8 HI4R. Kanaan started off the season with a third-place finish at the season-opening Toyota Indy 300 at Homestead-Miami Speedway. At the Indianapolis 500, Kanaan qualified on the pole position. In the race, Kanaan battled early with Sam Hornish, Jr. for the lead. Kanaan led for 54 laps, only to drop to an eighth-place finish in the final 50 laps of the race. Kanaan later won the Argent Mortgage Indy 300 at Kansas Speedway and the Argent Mortgage Indy Grand Prix at Infineon Raceway. Kanaan finished second in the point standings behind his teammate and friend Dan Wheldon with 548 points. In September 2005 Kanaan tested a BAR-Honda Formula One car for British American Racing at Circuito de Jerez as a reward for winning the 2004 IndyCar Series championship in a Honda powered car.