"What happened to 'there's no black America, there's no white America, there is just America?'" he said. A longtime friend of Donald Trump's, Giuliani also vigorously defended the candidate's character, saying he was "sick and tired of the defamation of Donald Trump by the media and the Clinton campaign."
He gotten the biggest cheers of the night from the crowd of more than 2,000 delegates.
** Click on the video player above to watch Guiliani's full, 15-minute speech **
Giuliani has been critical of those who protest against police, including those involved with the group Black Lives Matter.
He says when police officers "come to save your life, they don't ask if you are black and white, they just come to save you."
Guiliani also referenced New York in his speech.
"What I did for New York, Donald Trump will do for America," he said.
He also called Donald Trump "a man with a big heart" who's helped out their native New York City. He says Trump would anonymously help the families of police officers who were injured in the line of duty.
The Associated Press contributed to this report.