Egyptian-born Qaradawi, 86, has been invited to visit next month by the Union of Islamic Organisations in France (UOIF).
"I told the emir of Qatar himself that this gentleman was not welcome in the territory of the French Republic," Sarkozy told France Info radio.
Qaradawi, who hosts a popular show on Al-Jazeera satellite television, backed Arab Spring uprisings in Tunisia, Egypt and Libya, and has launched a fund-raising effort for the Syrian opposition.
He had been due to attend the UOIF congress at Le Bourget near Paris on April 6 alongside renowned Egyptian preacher Mahmud al-Masri.
"I said that a certain number of people, who have been invited to this congress and who maintain or who would like to take positions that are incompatible with the republican ideal, would not be welcome," Sarkozy said.
Qaradawi, who has close ties with the leadership of Egypt's Muslim Brotherhood, left the country in the 1960s after being imprisoned by the regime of president Gamal Abdel Nasser.
He is accused of having made anti-Semitic and homophobic statements and was banned from entering Britain in 2008. He has been banned from entering the United States since 1999.