The Matrix star Reeves spun into the grass without a crash on the exit of turn nine, a little more than halfway through the 45-minute race on Saturday.
He re-entered and continued driving, signalling he was uninjured.
Reeves is driving the No 92 BRZRKR car, which is promoting his graphic novel The Book Of Elsewhere. (AP PHOTO)
Reeves, who qualified 31st out of the 35 cars, ran as high as 21st and successfully avoided a first-lap crash at turn 14. He finished 25th.
Reeves, 60, is competing at Indianapolis in Toyota GR Cup, a Toyota spec-racing series and a support series for this weekend's Indy 8 Hour sports car event. He has a second race on Sunday.
Reeves is driving the No 92 BRZRKR car, which is promoting his graphic novel The Book Of Elsewhere.
Reeves has previous racing experience, taking part in the Toyota Grand Prix of Long Beach celebrity race. Reeves won the event in 2009.
He will attend a 30th anniversary screening of Speed on Tuesday in Los Angeles alongside his co-star Sandra Bullock.