AP
Tillerson's connections to Russia have already been called into question. He has no previous government experience or experience working as a diplomat and his ties to Russia that go back nearly two decades. Tillerson first met Russian President Vladimir Putin in 1999, according to Bloomberg, when Tillerson first represented Exxon's interests in Russia while it was under Boris Yeltsin's leadership.
Now some experts are calling attention to Exxon's business deals that could affect how Tillerson does business as America's top diplomat.
Several of Exxon's projects in Russia - worth tens of billions of dollars - have been put on hold because of sanctions the US has imposed on the country, according to The New York Times.
The US increased sanctions on Russia after the country annexed Crimea, which had been part of Ukraine.
Former Exxon board member William W. George told The Wall Street Journal that Tillerson opposed the additional sanctions at the time.
"As secretary of state, he would be called upon to negotiate with world leaders like Vladimir Putin," Michael T. Klare, a professor at Hampshire College and the author of "The Race for What's Left," a book about the rush for oil in the thawing Arctic, told the Times.
"In these negotiations, one has to wonder what would influence the types of deals he is making. Questions arise over whether his actions would be benefiting his company or the interests of the United States and its allies."
Tillerson owned $218 million in Exxon stock this year, according to the Times. He has worked for the company since 1975.
And one of the deals that helped catapult Tillerson to the highest ranks of Exxon was one he negotiated with Putin. The Wall Street Journal noted that Putin helped Exxon with an oil project on the Pacific Ocean island of Sakhalin that had been bogged down by bureaucracy for years.
President-elect Trump's relationship with Russia was a frequent topic of criticism during the campaign. Putin and Trump publicly praised each other, and Trump frequently said he hoped the US could work more closely with Russia.
"The real issue with Rex Tillerson's candidacy is going to be about Donald Trump's unusual views of Russia," R. Nicholas Burns, a former top State Department official in the George W. Bush administration, told the Journal. "Will the Trump administration, the president he serves have a rational, tough-minded approach to Russia? Right now, I don't see it."
Other experts disagree.
Ian Bremmer, president of the Eurasia Group, suggested that Tillerson's Russia connections could actually be a good thing for the US.
"As an oilman, Tillerson, like Trump, will take a very transactional approach to Putin," Bremmer wrote this week. "Some good may come from that. At the very least, it will produce better results for the US than Obama ever got from Moscow."