After briefly introducing the essential and original features of the personalist principle that is embraced by the Italian Constitution, the paper considers the work of the Constituent Assembly in which, in spite of its undoubtedly Catholic origin, the substance of the personalist principle was fully endorsed by the other ideological and cultural groupings present within the Assembly. It then goes on to examine the potential of the principle and how it has been understood and implemented in Italy within republican legislation, as well as constitutional case law.