A method for monitoring an epicyclic gear train of an aircraft includes the following steps: acquiring, at a predetermined sampling frequency, first values (5(ti)) of a signal formed by a progressive mechanical wave generated in the epicyclic gear train; measuring, at a plurality of successive instants, values (Vmes _r(tj)) of a speed of rotation of at least one of the toothed wheels of the gear train; calculating values (Vc(tj)) of a speed of rotation of a point of contact between two toothed wheels of the epicyclic gear train; determining second values (S(ç½)) of the signal formed by a progressive mechanical wave generated in the epicyclic gear train, the second values being sampled depending on a phase of the point of contact and forming secondary mechanical wave data; and using the secondary mechanical wave data (S(ç½)) to detect an anomaly related to the operation of the epicyclic gear train.