The Scuderia qualified only ninth and 11th for the race last season but Leclerc and team-mate Carlos Sainz showcased the year on year improvements by finishing Friday's running third and eighth.
When asked if it had been "immediately obvious" the steps forward made by the team when taking to the track in Barcelona, Leclerc said: "Definitely. last year, I think we were struggling quite a lot and it feels like the car is in a much better place this year.
"I think it is especially good for the team back in the factory who can see the numbers and how much better we are than last year, it motivates everyone so it feels good in the car and hopefully tomorrow will be a good day."
Leclerc struggled throughout the weekend in Portimão last time out but managed to recover during the race to finish sixth, five places ahead of Sainz.
To prevent a repeat of these difficulties, the Monegasque driver revealed he has altered his driving style.
He added. "I changed my approach a little bit compared to Portimão, taking it more step by step and just driving a lot better and in a better place with the car.
"Hopefully, we can keep building on that string first day for tomorrow. It will be important in qualifying for this track.
"We know where to improve so now let's see if we can do a good job just by getting better where we are struggling."
GPFans is a multi-platform, multi-language brand dedicated to Formula One coverage. We bring you all the ins and outs of the sport, 24/7, everything from up-to-the-minute news and features to the latest viral stories and clips.
We believe that a new generation of exciting, outspoken drivers will make F1 more popular than ever before, and we want to give our users access to as much of their heroes as possible, on and off the track. From Lewis Hamilton to Max Verstappen, Daniel Ricciardo to Sebastian Vettel, we provide in-depth analysis of every every Grand Prix in the season, from Australia to Abu Dhabi.
With Formula One under the new ownership of Liberty Media, how the sport is being covered is evolving, and GPFans will look to be at the heart of this progression into new media, as one of the fastest-growing sites covering the king of motorsports.