Brussels accused Google of giving its own service too much priority in search results to the detriment of other price comparison services, such as TripAdvisor and Expedia.
The search engine giant filed an appeal Monday against the European Union which fined the company for favoring its own shopping ads over its competition.
Google said it had no further comment.
However, setting up a court battle between Brussels and the internet giant could take years to resolve and make already tense relations between Europe and the U.S. tech giant even more fraught, AFP reported.
Google had been given 90 days to stop the favouritism or face a penalty of up to 5% of the average daily turnover of its parent company Alphabet.
Intel Corp. waited eight years for a ruling on its legal challenge to a 2009 fine only to be told last week that the General Court must re-examine the case.
"Google's strategy for its comparison shopping service wasn't just about attracting customers by making its product better than those of its rivals", commissioner Margrethe Vestager, who is in charge of competition policy, said when June's decision was announced.
Regulators are also expected to levy fines in separate investigations into Google's Android mobile-phone software - possibly as soon as next month - and the AdSense advertising service.
The appeal, which the court has confirmed receiving, will take some time to be heard and is likely to result in prolonged expensive hearings, but an unapologetic Commission on Monday insisted that it will "defend its decision in court".