The Associated Press obtained the ruling on Wednesday. It came in response to an appeal by Chevron seeking to nullify the judgment.
Chevron has refused to pay the plaintiffs in the case, claiming fraud, and has tied them up in courts and arbitration panels on three continents.
The local lawyer for the plaintiffs, Pablo Fajardo, told the AP that while he regrets the court halved the financial penalty, it "completely ratifies the sentence against Chevron for the environmental crime committed in the Ecuadorean Amazon. I think that after 20 years of fighting we are seeing light at the end of the tunnel."
A spokesman for U.S.-based Chevron, James Craig, called Tuesday's ruling "just as illegitimate and unenforceable today as it was the day it was issued three years ago."
Chevron claims a cleanup agreement signed in 1995 by Texaco released the oil giant from financial responsibility from any damage claims.
Chevron has no assets in Ecuador, so the plaintiffs have sought to force payment in Canada, Brazil and Argentina, so far without success.