Microsoft is investigating whether Russians bought ads on any of its products or platforms, including its Bing search engine, in an attempt to sway the US election result.
A spokeswoman for Microsoft gave no further details.
The move comes after rival Google said Russian operatives bought ads on YouTube, Gmail and Google Search in an effort to influence the election.
Google runs the world’s largest online advertising business and its revelation increased fears that US tech companies may have unwittingly played a role in the election of Donald Trump.
Google said in a statement: “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 ads on Google were not from the Kremlin-linked group that bought ads on Facebook, according to a report in the Washington Post.
US intelligence agencies said earlier this year that Russia had tried to sway the election in favour of Mr Trump but the Russian government and Mr Trump have both denied this.
There are a number of Congressional investigations into the alleged Russian interference.
Google has been invited to testify before both the House and Senate intelligence committees next month.
Facebook and Twitter, whose officials were also invited, have confirmed they will attend but Google has not responded.