"He has not told me what he found, but I think he wants to go before Congress ... and also to the attorney general and the Department of Justice," he added. "I hear he has found plenty."
Guiliani visit to Ukraine this week raised eyebrows as it comes at a time when the House is conducting an impeachment investigation into whether the president abused his power.
The Democrats have accused Trump of misusing power by asking Ukraine to conduct investigation against his political rival Joe Biden and his son Hunter.
Giuliani, during his trip, met with multiple Ukrainian officials as he continued his campaign to convince American lawmakers that Trump did nothing wrong.
Giuliani said Thursday that a probe into Biden is "a major obstacle to the US assisting Ukraine with its anti-corruption reforms.