In a private meeting on Wednesday at the Hôtel Matignon, the prime minister's official residence, he told a group of elected officials he was planning to run.
"As it's just us, I will tell you a secret," he said. "When the time comes I will be at your side to lead the legislative campaign in Paris."
Many have believed for a long time that Fillon would run for a seat in 2012 and then for the job of mayor of Paris when elections come up in 2014. The current mayor of Paris is Socialist Bertrand Delanoë.
After the failure of the governing UMP party in recent elections to the Senate, when the Socialists won their first ever victory, pressure has grown on Fillon to announce his candidature.
He is believed to be lining up for the seat in Paris' wealthy 2nd constituency which covers a large chunk of the left bank of the city, home to the Latin quarter.
Rachida Dati, the former minister of justice, is also believed to be eyeing the seat. She was part of Fillon's government until 2009 when she left after taking a seat in the European parliament.
57-year-old Fillon has been prime minister since Nicolas Sarkozy came to power in May 2007 and has consistently had a higher satisfaction rating than the president. He is married to a Welsh woman, Penelope, and they have five children.
Nicolas Sarkozy's predecessor, Jacques Chirac, used the mayor of Paris job as the platform for his successful run for the presidency in 1995. Chirac also served as prime minister, from 1974 to 1976, before taking the mayor role between 1977 and 1995.