He also made unsubstantiated claims that some of the votes could have come from dead people and Canadians.
The former mayor also said that Philadelphia had a history of "voter fraud".
Giuliani also said that the "elite" were trying to "steal" the election.
In an embarrassing comment on the validity of Giuliani's claims, Trump's favourite news network Fox interrupted the former New York mayor with their call that Biden had won the battleground state of Michigan.
"Do you think we're stupid? Do you think we're fools?" asked Giuliani, before Fox host Neil Cavuto cut him off to announce the result.
Meanwhile, President Trump has claimed the state of Michigan, despite major networks giving it to his rival and announced he is also claiming Georgia, North Carolina and Pennsylvania.
Giuliani has been a controversial figure in recent years, often appearing on television to make claims about Joe Biden and his son Hunter.
But his appearance in the recent Borat film was his most scandalous on-screen appearance, with the bombastic lawyer being caught in a sting in a hotel room.
Rudy Giuliani is shown with his hand down his pants after flirting with an actress playing a young woman pretending to be a television journalist in a scene in Sacha Baron Cohen's latest mockumentary, a sequel to his hit Borat film.
The scene shot in a New York hotel room in July — which resulted in Giuliani calling police — includes a moment when Giuliani is seen lying on a bed with his shirt untucked and his hand down his pants with the young woman nearby.
Giuliani went to the hotel room thinking he was being interviewed about the Trump administration's Covid-19 response. The young woman is flirtatious with him and invites him to the bedroom, which is rigged with hidden cameras.
Giuliani then asks for her phone number and address. He lies back on the bed and has his hands in his pants.
The hotel room scene ends when Baron Cohen, who was disguised as part of the crew, bursts into the room in an outlandish outfit screaming that the young woman is 15 years old. Up to that point, there is no indication she is underage.
The character, Borat's daughter, is played by actress Maria Bakalova, who is listed as 24 years old on the Internet Movie Database site, IMDb.com.
Speaking on his weekly radio program on WABC, Giuliani called the scene "a hit job."
"At no time before, during, or after the interview was I ever inappropriate," Giuliani tweeted. "If Sacha Baron Cohen implies otherwise, he is a stone-cold liar."
The former New York City mayor called police after that encounter, but there is no indication an investigation was launched. Giuliani spoke to the New York Post's Page Six column about the incident in July, but did not mention the bedroom aspect of the encounter.
- Additional reporting, AP
