A method and a device (D) for detecting and signaling the approach to a vortex domain by a rotorcraft, the device includes: first elements (1) for measuring the instantaneous vertical speed v of a rotorcraft; second elements (2) for measuring the instantaneous proper airspeed VP of a rotorcraft; third elements (3) constituting a database BDD relating to representing at least one instantaneous vortex domain; fourth elements (4) connected via first, second, and third connections (l1, l2, l3) respectively to the first, second, and third elements, the fourth elements being designed to detect the approach to a vortex domain by the rotorcraft; and fifth elements (5) for signaling the approach to a vortex domain by the rotorcraft, the fifth elements being connected to the fourth elements (4) via a connection (l4).