Can we speak of “system” about Leibniz’s conceptuality? According to the contemporary studies on Leibniz, clearly, the notion of system cannot be used to speak about Leibniz because his thinking involves a lot of aspects and never forms a single complete coherent whole. However, some occurrences of the word “system” in Leibniz’s texts and, more generally, the way Leibniz tries to embrace a detailed and global approach may lead to consider the Leibnizian thinking as an immutable structure that is self-justified, that is to say, as a system in the philosophical meaning. In that sense, how speaking of “system” about Leibniz’s conceptuality? Because, on the one hand, we cannot deny that Leibniz evolved a lot in his conceptuality, so, as the contemporary Leibnizian philosophers say, his thinking cannot be comprehended as a system. But, on the other hand, in a few occurrences, Leibniz himself seems to present his thinking as an immutable structure that is self-justified, that is to say, as a system in the philosophical meaning. In order to reconcile the problematic confrontation of both approaches, in a first time, we will see why it may be tempting to make the Leibnizian mature philosophy a philosophical system. But, in a second time, we will see that such a reading is a kind of Bergsonian “mouvement rétrograde du vrai” if we consider the whole Leibniz’s work. And, finally, we will try to propose a meaning of “system” that may match with Leibniz’s approach.