But lawmakers still said they have concerns about the incoming administration's Russia policy.
Senators and senate aides from both parties said that Tillerson made a good first impression in his meetings this week, but they were still looking for a clear statement on Russia during his testimony next week.
"He is at heart a conservative businessman, with a worldview that has been shaped by mainstream Republican principles," one aide told CNN. "Every nominee has to contend with how their views fit in with the administration they are entering, but with Tillerson, I think an important question next week will be at what point do his moral convictions and what he knows to be true contrast with the president he is about to serve?"
Several sources said that Tillerson projected a clear-eyed view toward Russia, including the need to get tough with President Vladimir Putin.
"He indicated that he knew what Putin was about and that you need to deal with Russia from a position of strength. He framed his relationship with Putin as one where he felt he could talk to him frankly and that he was prepared to do that," another staffer told CNN. "He gave good answers and I can say the tone was encouraging."
Sen. John McCain, who described his meeting Wednesday with Tillerson as "good" and productive," said he had additional questions and concerns about Russia he hoped Tillerson would address.
"He satisfied some of my concerns," McCain told reporters Wednesday, but added, "I have additional concerns."
Sources said Tillerson would not be drawn into the ongoing dispute between the President-elect and the intelligence community over Russian interference in the US presidential election and avoided discussing specific policies the incoming Trump administration may pursue.
While he voiced skepticism as CEO of ExxonMobil about the effectiveness of sanctions, Tillerson acknowledged in his meetings with senators that sanctions could be a useful policy tool, although he declined to endorse any particular sanctions.
Senate Foreign Relations Committee Chairman Bob Corker said Tillerson's views on international relations -- including Russia -- are very much in the "mainstream of foreign policy thinking here in the US."
Corker, who will oversee Tillerson's confirmation hearings, met with the former ExxonMobil chief executive Tuesday.
Asked if he expects Tillerson, who has a relationship with Putin and has cut business deals in that country, will lead a robust policy towards Russia, Corker said yes. That's been a key concern of several GOP senators, including McCain.
"I had a long private conversion with him. I had talked to him on the phone prior to that," said Corker, who was also reportedly under consideration by Trump for the secretary of state position. "I think what people are going to find when they hear Tillerson in the hearing is that he's very, very much in the mainstream of US foreign policy thinking."
Senate Democrats were also heartened by Tillerson's comments about climate change and his support of climate science.
"He stressed, for me, his background in science and that he is a believer in science," said Sen. Ben Cardin, the ranking Democrat on the Senate Foreign Relations Committee after his meeting on Wednesday. "That also was encouraging. So we did have a rather, I think a lengthy discussion about climate change issues and the importance of conservation and what we need to do in countries around the world where extreme poverty has denied many people access to a reasonable energy accessibility."
Sen. Chris Coons, another Democrat on the committee, said he was "generally encouraged" by some of Tillerson's answers during their meeting, as well as his openness and humility, but had not decided whether to support his nomination.
Tillerson is expected to give two days of testimony next week. Before then, senators and their aides are combing over documents he has provided to the committee.
Although he didn't provide his tax returns, he did provide an extensive financial disclosure and ethics agreement. Senate aides say they are closely reviewing a plan ExxonMobil released this week to pay out Tillerson's holdings in the company -- which will net him about $180 million to be put into a blind trust. He also provided various speeches he had given as CEO of ExxonMobil and information on legal cases the company faced under his leadership.
Despite Tillerson's impressive performance, senators and aides said concerns linger about the incoming administration's Russia policy, which was expected to be a focus of his confirmation hearing next week.
"Russia is not a friend of the United States. We have serious concerns about Russia. I think that's a strong bipartisan message that you're going to hear during the confirmation process," Cardin said. "Obviously, he did business with Russia. He was able to get things done there and those relationships will be subject to questioning during the confirmation hearings."
Another senator wary of Russia conceded that "Tillerson wasn't the problem," but warned that Trump's refusal to acknowledge Russia's interference in the election could slow his confirmation.
"If Trump has an intelligence briefing on Russia on Friday and still denies the intel pointing to Russia is reliable, we are going to have a problem," the senator told CNN. "Trump's nominees will have to pick sides -- between the intel and Trump."