The foundation of morality, and mainly, the possibility of moral sentiments that are universal and inalienable, is a central problem in Maine de Biran’s philosophy. Many studies focus on the part played by the self in Maine de Biran’s late philosophy, but relatively few consider with precision the importance of the concept of sympathy in this context. In this paper, I would like to show that this concept, which Biran mobilizes from his first to his last writings, is an important conceptual resource in his enterprise of founding morality. I will draw on three main texts that cover almost the entire period in which he wrote, namely, his Mémoire sur l’influence de l’habitude sur la faculté de penser ( 1987), his Mémoire sur les perceptions obscures ou sur les impressions générales affectives et les sympathies en particulier ( 1984), and his Fragments relatifs aux fondements de la morale et de la religion ( 1859). The main finding is that sympathy occupies a central place in this enterprise of moral foundation but undergoes profound and almost contradictory conceptual re-elaborations throughout Biran’s intellectual journey. Although in his first philosophical texts Biran concentrates on the fundamental dimension of organic sympathy, he rejects it almost entirely in his last texts in favor of an analysis of the sympathy between the selves.