The paper proposes a brief analysis about the Leonardo’s contribution to the birth and the maturation of the modern engineer–architect. We have considered the influence of ancient mechanics and ‘devices costructors’ of the early Renaissance on his research and scientific divulgation, as well as the important methodical imprinting left by this great ‘scientist–artist’ in the professional environment during the contemporary age. In fact, since the end of the 18th century the role of the new ‘scientist–artist’ — the State engineer in charge of public architectures and infrastructures — became prominent after the establishment of the Polytechnic Schools, having its roots in the complete Leonardo’s professional figure, before the definitive split between architect and engineer in the early 20th century.