Method and device for assisting with landing an aircraft under poor visibility conditions are provided. The method allows sensor data to be received during a phase of approach toward a runway when the runway and/or an approach lighting system are not visible to the pilot from the cockpit; then, in the received sensor data, data of interest characteristic of the runway and/or the approach lighting system to be determined; then, on the basis of the data of interest, the coordinates of a target area to be computed; and, on a head-up display, a guiding symbol representative of the target area to be displayed, the guiding symbol being displayed before the aircraft reaches the decision height, in order to provide the pilot with a visual cue in which to search for the runway and/or approach lighting system.