The encounter is just one example of the president ignoring the advice of his attorneys and asking witnesses about their interviews with the special counsel's team regarding the ongoing probe.
During their conversation, Trump asked Priebus if the special counsel's team had been "nice" and if he was treated fairly, according to the source. The source described the encounter as a small portion of a larger conversation about other topics.
The New York Times was first to report the interactions between Trump and members of his team, including Priebus and White House counsel Donald F. McGahn II.
Priebus and McGahn's lawyer, declined to comment. Lawyers for the president have not responded to ABC News.
Sources close to the president said they do not believe this could be deemed as any form of witness intimidation because the conversations happened after the individuals met with the special counsel team and were not substantive in nature.
However, the timing comes as the president's legal team is in active negotiations for what the president will do with the Mueller team, which could include an in-person interview -- but no final decisions have been made.