Ferrari Driver Academy products Giuliano Alesi, Marcus Armstrong and Robert Shwartzman took to the track on Monday in the 2018 SF71H, but on Tuesday Ferrari declared its season "properly underway" when Leclerc got behind the wheel.
Just 44 days after the season-ending Abu Dhabi Grand Prix last year, Leclerc said: "Getting back in the car today was great, in fact, it was brilliant.
"Seeing my mechanics again, putting the race suit on, doing my warm-up routine, putting on my helmet and finally jumping in the car and pressing the starter button… the sound of a Ferrari engine is always magic.
"The day was simply perfect and we got through all the work we had planned to do. I really enjoyed myself! Now I hand over to Carlos [Sainz] and I wish him the best of luck for tomorrow."
Pre-season testing has been reduced from the usual six days to just three this year as a result of cost-saving measures brought in to protect teams from the financial damage of the coronavirus pandemic.
It has led to the likes of Ferrari opting to provide drivers with track time in older machinery.
The Monégasque driver completed over 100 laps and performed numerous practice starts across the day whilst "reacquainting himself with procedures and driving a Formula 1 car".
Watching in the wings was Sainz, who will conduct his first laps for the Scuderia on Wednesday, with additional track time on Thursday morning.
Haas driver Mick Schumacher will drive the car on Thursday afternoon and Friday morning, while test driver Callum Ilott is scheduled to run on Friday afternoon.
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