Sauber star Leclerc, who joins Sebastian Vettel at the Scuderia in 2019, completed 129 laps behind the wheel of the SF71H at the French Grand Prix venue. Vettel will drive the car tomorrow.
It marked the first time Leclerc has driven for Ferrari since being announced as a race driver for next year.
The test is viewed as crucial for Pirelli, as the F1 tyre supplier approaches the conclusion of its 2019 development programme. Leclerc shared the track with the Mercedes of Valtteri Bottas, who completed 102 laps.
Both teams had already conducted 2019 wet test days for Pirelli, but this was the first time that they have run the new slicks. The tyres were unbranded, so teams did not know which construction nor compound they were running.
The remaining tests, with Renault after the Japanese GP and Sauber after the Mexican GP, will focus on compounds.
The definitive tyres will then be run by all teams immediately after the Abu Dhabi GP.
Additional reporting by Adam Cooper