It is the first time Microsoft - itself the target of anticompetition action in the United States and Europe - has filed a complaint with regulators over competition issues.
In its complaint on Thursday (31 March), Microsoft claims Google engages in a "pattern of actions" that unfairly impede competition.
Google controls more than 90% of the Internet search advertising market in Europe, well ahead of Microsoft's Bing, which is struggling to make inroads into Google's market share.
Microsoft Corp. stepped up its rivalry with Google Inc. with a formal complaint to EU antitrust regulators, claiming Google systematically thwarts Internet search competition.