"Overall, it was a good session and now we need to carry on this performance through the weekend". That victory erased a 14-point lead held by Hamilton after he could manage only a fifth-place finish.
Mercedes introduced their upgraded spec 2.1 engine for the French GP and it clearly made a difference as Ferrari were unable to close the gap on the leaders despite the Italian team being known to turn up their engines for the final part of qualifying just like their rivals.
The 28-year-old Finnish driver conceded that his final qualifying lap was not ideal and with Hamilton still out on track "you can never be sure", he said. "It's really, really great to have this result, and a one-two".
Leclerc pulled out a stunning late lap to go tenth overall and he pipped Esteban Ocon to the final spot in Q3 as both Force Indias failed to progress.
Having wrestled the championship lead back from rival and reigning champion Lewis Hamilton, Vettel is looking to build some momentum with the first ever triple header in Formula 1 history - France, Austria and the United Kingdom all being run on consecutive weekends - and remains confident of his chances on race day in Paul Ricard. I don't know why but l keep getting to Q3 and it's just not happening.
"After the first attempt I saw that we were maybe there so I knew that with a really wonderful lap I would maybe have a chance but it didn't come. That's frustrating. In the whole session l had half a second on everyone and with pole it was "phew, job done", but it was only a tenth and that doesn't look good on your CV!"
Ferrari's Sebastian Vettel was third, ahead of Red Bull's Max Verstappen. "But a fresher, newer version of that is going to be great, and have more power than the one I raced in the last race, obviously. But already at the beginning I tried to push hard and probably pushed a little bit too much so I lost a little and then you're playing catch-up".
"The new engine feels clean and fresh", said Hamilton. "There were great discussions where the team was able to be open with each other, and say honestly, 'This could be better.' About each other as well, and things that I know I can do better, which I'm planning to do". "They must be confident". They are like, 'Oh, you can't say that.' But [it's a case of] 'No, I thought we said we're in that comfort zone, you can say what you want.' Naturally, everyone is shedding their blood, sweat and tears to make sure we win this season.