Following the private meeting, Graham told reporters that he doesn't believe Whitaker will do "anything unsavory" when it comes to interfering with the Russia probe.
"I've a lot of confidence that Mr. Mueller will be allowed to do his job and that the legal process that was in place before Mr. Whitaker arrived will be followed," Graham said.
He went on: "And I have every confidence he’ll make reasoned decisions when his time comes and that the investigation is not in jeopardy."
Graham also says Whitaker did not express any reservations about how the Mueller investigation was handled thus far.
"Not at all as far as he knows, no, not at all," Graham said. "He’s seen nothing out of bounds. No concerns at all about Mr. Mueller."
In his new role, Whitaker will now oversee the probe, which he has publicly criticized the probe in the past, including in an August 2017 op-ed for CNN. Sessions had previously recused himself of all Justice Department activity related to the investigation into Russian meddling.
Now, lawmakers are concerned that Whitaker’s objectivity is compromised because of his vocal criticism before joining the administration.
Despite calls from Democrats for Whitaker to recuse himself from overseeing the Mueller probe, Graham separately told Fox News that Whitaker doesn't feel the need to do so.
"He believed he did not have a reason to recuse himself legally or factually," Graham told Fox News. "Nothing I’ve seen would require him to be recused. I think he's got the background and the judgment to be able to fulfill this job."