The invention concerns a reversible headrest for passenger seat comprising two faces: a waking face to support the passenger's head when he is awake (figure 1C); a sleeping face to support the passenger's head when he is dozing or sleeping (figure 1B). The shift from the waking position to the sleeping position is achieved by a 180 degree-rotation about an axis (21) substantially parallel to the longitudinal axis of the seat back. Said rotation can be powered by an electric motor (63). The sleeping face comprises a rear surface (3), an inner lateral edge (5), an outer lateral edge (6), a front lateral edge (8) adjacent to the edge (6). The length of the outer lateral edge (6) is not less than the diameter of the average passenger's head. A safety device releases the rotation of the headrest or of the edge (6) when the edge (6) is subjected to a couple of forces greater than a predetermined value.