Hornish began driving in the IndyCar Series in 2000 for PDM Racing in the No. 18 G-Force GF05-Oldsmobile Aurora L47 V8. He debuted at the season-opening race at Walt Disney World Speedway, starting in 19th place and finishing in 20th (28 laps behind). In the season's third race, the Vegas Indy 300 at Las Vegas Motor Speedway, Hornish started 18th and had his first career podium finish (third place, one lap behind). He qualified for his first Indianapolis 500 in 14th place, after his team replaced the G-Force with a Dallara IR00. In mid-race, Hornish was involved in an accident which relegated him to 24th place. Starting 20th at Kentucky Speedway, he led for a series career-high 38 laps and finished ninth. Hornish ended his season with a 27th- (and last-) place finish at Texas Motor Speedway, finishing his rookie season with 110 points (21st in the point standings).