The company has made agreements with electronics manufacturers Apple and Samsung to make Google's search engine the default search engine in their browsers.
A federal court in the District of Columbia has ruled that Google abused its market position to maintain a monopoly in search engine and online advertising, the court said in a ruling.
Federal Judge Amit Mehta ruled that Google blocked about 90% of the Internet search market for competitors by entering into an agreement with Apple that made Google the default search engine in its Safari browser. The corporation has similar agreements with Samsung and telecom operator Verizon.
Mehta added that Google put Microsoft at a "disadvantage" in the market for ads displayed next to search results, allowing it to become a monopoly in this area as well.
Earlier, the US Justice Department filed a lawsuit against Google for violating antitrust laws.
In July, Ilon Musk said that Google was interfering in the US presidential election.