Trump's legal counsel, Jay Sekulow, announced the move in a statement.
"The president said, 'Rudy is great. He has been my friend for a long time and wants to get this matter quickly resolved for the good of the country,'" Sekulow, said according to Newsday.
Giuliani said the appointment was "an honor."
Trump added two more federal prosecutors to his legal team -- Serene Raskin and Marty Raskin.
"Jane and Marty are highly respected ... with decades of experience," Sekulow said, according to USA Today. "They have a nationwide practice and reputation for excellence and integrity."
The additions come nearly one month after the resignation of John Dowd, the former personal attorney to Trump for matters relating to Special Prosecutor Robert Mueller's investigation into alleged Russian interference in the 2016 presidential election.