Leonardo targeted Champions League football after finally being presented as the new sporting director of Paris St Germain.
Leonardo, 41, left his post as coach of Inter Milan last month having long been linked with a switch to PSG, where he spent a year of his playing career, but it has taken some weeks to formalise his move to the Ligue 1 club.
As he was unveiled to the press, he said: ''I'm really happy to be here. I have strong memories from my 14 months in Paris. I always thought I could come back but I did not know it would be like this. 'It was not easy for me to leave Italy. In Paris there is much to get to grips with, to do; the club has been bought.
''This club is 41 years old. It's a big club. The owners want to work in the long term. We do not want to buy 10 Messis, that's not how you build a team. You need a base. It exists and must be improved.
''We want to play in the Champions League and be good domestically. I think the first thing is to talk with the coach and see who will stay or leave. The transfer window ends on August 31. It's not a project aimed at winning the first game but for the long term. I have to study and, slowly, build a project.''
Antoine Kombouare remains as coach at the Parc des Princes under new owners Qatar Sports, who bought a 70% stake last month.
Leonardo joined Inter in December after leaving AC Milan six months earlier and led the team to a runners-up finish in Serie A and Coppa Italia glory. He was replaced by Gian Piero Gasperini last month with the move to PSG on the horizon.
He joins a team who finished fourth in Ligue 1 last season and will play in the Europa League this term.
Much will be expected of them this season with the backing of Qatar Sports giving them the sort of funds which should lead to a title challenge.
Also, PSG announced the departure of president Robin Leproux after two years in the role, with former financial director Benoit Rousseau taking over on an interim basis.