The company, which manufactures plastics used in household appliances, appealed the €9m fine which was imposed in 2006.
The European Commission had taken the case against a number of European companies which it accused of operating a cartel in the 1990s.
The companies were accused of discussing prices, agreeing, implementing and monitoring price agreements and the exchange of commercially important and confidential information.
The case dates back to the 1990s when executives were accused of meeting in a Dublin hotel to exchange sensitive data and fix prices. Following today's judgment the fine was reduced to €8.25m.
Earlier this year, IBRC, the former Anglo Irish Bank, appointed a share receiver to take control of the Quinn family's stake in Quinn Group, which includes the glass business.