After talks with NTC leaders in Tripoli, they will fly to the western city of Benghazi to give a speech in Liberty Square, reported the BBC.
Fighting is still ongoing in pro-Gaddafi strongholds, but NTC chief Mustafa Abdul Jalil said that both men's safety would be ensured.
Britain and France led the Nato operation that helped Libya's rebels oust dictator Muammar al-Gaddafi – and Cameron and Sarkozy are now the most senior world leaders to visit since his overthrow.
Cameron and Sarkozy are hugely popular in Libya, where common graffiti slogans are "Merci Sarkozy" and "Thank you Britain".
Al Jazeera described Thursday's visit as “a victory lap” for Sarkozy and Cameron, whose ability to secure Libya was widely doubted.
The network's correspondent said their visit was "all about building confidence".
Of course, France and Britain took leading roles in the intervention in Libya, but it's much more important now that in this post-Gaddafi period ... France and Britain be also seen to be leading the recovery.
Jalil has warned that Gaddafi is still in the south of Libya, planning revenge attacks – and he appealed for weapons to be provided, to allow NTC forces to take control of Bani Walid and Gaddafi's hometown of Sirte.
Meanwhile, Turkish Prime Minister Recep Tayyip Erdogan is expected to visit Libya on Friday, while Egypt's Foreign Minister, Mohammed Kamel Amr, is also planning to visit.