Russian operatives spent tens of thousands of dollars on ads across Google products, including YouTube and Google search, according to reports.
The Washington Post reports that the technology behemoth uncovered the Russian-backed disinformation campaign as it considers whether to testify before Congress next month.
Social media giants Facebook and Twitter have already agreed to testify.
The report said the company discovered the Russian presence by siphoning data from Twitter.
Gmail and the company's DoubleClick ad network were believed to be impacted, the newspaper said.
The Washington Post report is based on anonymous sources familiar with the investigation.
In a statement, Google said it has a "set of strict ads policies including limits on political ad targeting and prohibitions on targeting based on race and religion".
"We are taking a deeper look to investigate attempts to abuse our systems, working with researchers and other companies, and will provide assistance to ongoing inquiries," the statement continued.
Facebook recently shared about 3,000 Russian-backed ads with Congress.
US intelligence agencies have concluded that Russian President Vladimir Putin directed a disinformation campaign aimed at helping Donald Trump win the presidential election.
YouTube recently removed Russian TV outlet RT from its advertising network.
The channel's deputy editor-in-chief Kirill Karnovich-Valua asserted in response that the move was an attempt to force the channel out of the American market.