"I have been sitting here looking in the federal code trying to find collusion as a crime," Giuliani said in an interview on Fox News Channel's "Fox & Friends." "Collusion is not a crime."
Trump has repeatedly denied there was collusion between his campaign and Russia during the 2016 U.S. presidential election. As recently as Sunday, the president took to Twitter to repeat the claim.
"There is No Collusion!" Trump wrote, referring to special counsel Robert Mueller's investigation into Russia's attack on the election.
Giuliani expanded on his remarks in an interview with CNN. "The hacking is the crime," Giuliani told the network. "The president didn't hack."
Following the interview on CNN, Giuliani responded to a post on Twitter that suggested the media was "nitpicking and twisting" his comments.
Giuliani called the post an "excellent observation."
"You can investigate an innocent person forever and forever and find nothing. When do we say enough is enough. No collusion, no obstruction. President Trump did nothing wrong," Giuliani wrote in response.
Giuliani addressed reports that Michael Cohen, the president's former lawyer and fixer, was prepared to tell Mueller that Trump knew about a June 2016 meeting in Trump Tower between the president's senior campaign staff, including his eldest son Donald Trump Jr. and then-campaign chief Paul Manafort, and a Russian lawyer who was allegedly offering dirt on Democratic presidential candidate Hillary Clinton.
"This Russia meeting, I'm happy to tell them, he wasn't there," Giuliani said.
Before Giuliani's interviews Monday, the intrigue about the meeting centered on whether the elder Trump knew the meeting was going to happen. The president has previously denied foreknowledge of the gathering.
"I did NOT know of the meeting with my son, Don jr. Sounds to me like someone is trying to make up stories in order to get himself out of an unrelated jam," the president wrote in a post on Twitter on Friday.
The special counsel has homed in on the Trump Tower meeting, and has sought to ask Trump about how involved he was in its planning.
The meeting figured in a list of questions the special counsel prepared to ask the president. Among the questions, published by The New York Times in April, was an inquiry about when the president first became aware of the June 9 meeting.
Cohen's attorney Lanny Davis declined a request for comment from NBC News.
Giuliani also addressed the president's claims that Mueller has conflicts of interests. On Sunday, the president wrote in a post on Twitter that Mueller has "conflicts of interest" with respect to Trump, citing what he called a "very nasty & contentious business relationship."
Asked about that claim Monday on CNN, Giuliani declined to elaborate, but said that Mueller should "stand up and be a man."
"He has the conflict, not the president," Giuliani said, explaining why Trump should not have to defend his claim. "I can't tell you" what the conflict of interest is, Giuliani said. "I'm not sure I know exactly what the conflict is. I have a good idea what it is. It's one that would have kept me out of the investigation."
Trump has reportedly fixated on an allegation that Mueller in 2011 ended his membership at the Trump National Golf Club in Virginia after a dispute over the club's fees. Mueller's team has said that there was no dispute. Trump has also repeatedly claimed that the Mueller probe is being led by Democrats. Mueller and his boss, Deputy Attorney General Rod Rosenstein, are Republicans.
Giuliani's remarks came a day before Manafort goes to trial in Virginia over charges stemming from Mueller's probe.
Earlier this month, Mueller obtained an indictment against 12 Russian nationals for hacking into computers belonging to the Democrats during the 2016 election. The Russians were charged with conspiracy to commit computer crimes, among other violations.
So far, the special counsel has filed nearly 200 criminal charges against 35 defendants, according to a CNN tally. Five individuals have pleaded guilty.
The special counsel is examining potential improper ties between the president's campaign and Russia. He's also reportedly examining whether the president has obstructed justice. Rosenstein told the president that he was not a "target" of the investigation, Bloomberg reported in April.
The White House did not immediately respond to a request for comment.