The decision to prevent Mr. Giuliani to work as a lawyer was made by a disciplinary panel of lawyers in the state.
However, a former federal prosecutor said the suspension would likely prevent the former New York mayor from working as a lawyer in other areas as well.
The panel said there was “undisputed evidence” that Mr. Giuliani had made false statements to the courts, the public and politicians when he claimed that the election was stolen by fraud.
In its motion to suspend the license, the committee said: “This country is torn apart by continued attacks on the legitimacy of the 2020 elections and of our current president, Joseph R Biden.
“The hallmark of our democracy is based on free and fair elections. False statements aimed at promoting a loss of confidence in our elections and the resulting loss of confidence in government are generally detrimental to the proper functioning of a free society.
Mr. Giuliani worked as a lawyer for Monsieur Trump, and represented him in numerous court hearings as the Republican side sought to overturn Mr. Biden’s election victory.
The 77-year-old tried to claim a free speech defense for his false claims and said he did not knowingly make misleading statements, but that was dismissed by the panel.
They said Mr Giuliani had failed to “provide any evidence of any of the varying and extremely inconsistent numbers of deceased people he actually represented in Philadelphia in the 2020 presidential election.”
David Weinstein, a former federal prosecutor, said Mr Giuliani should notify other states of the suspension, which “will in all likelihood cause them to say, ‘You won’t be able to practice here.’
In addition to representing Mr. Trump in court, Mr. Giuliani has also given numerous press conferences, including one at the Four Seasons Total Landscaping in Philadelphia on the day Mr. Biden was named the winner.
Meanwhile, Mr Giuliani claimed there was a large Democrat plot that would be overthrown.
Attempts by the Trump campaign to overturn the election result resulted in the January 6 riots at the Capitol.
Mr Giuliani is separately under investigation for his interactions with prominent Ukrainian figures as he tried to get the country to open an investigation into one of Mr Biden’s sons.