A method for measuring an ultrasonic attenuation parameter guided by harmonic elastography including applying, using a vibrator included in a probe in contact with a viscoelastic medium, of a continuous low frequency vibration, the continuous low frequency vibration generating an elastic wave within the viscoelastic medium and generating, during the propagation of the elastic wave, using an ultrasonic transducer in contact with the viscoelastic medium, a series of ultrasonic acquisitions, the series of ultrasonic acquisitions including groups of ultrasonic acquisitions, the groups of ultrasonic acquisitions being generated with a repetition rate, each group of ultrasonic acquisitions including at least one acquisition; the ultrasonic attenuation parameter being measured from the ultrasonic acquisitions realised during the application of the continuous low frequency vibration.