The invention relates to a method for stabilizing a diode laser with a semiconductor laser diode and an external resonator (ECDL), wherein the external resonator is comprised of at least one angle-dispersive, frequency-selective element and wherein the frequency of the diode laser is essentially determined by the length of the external resonator and by the position of the angle-dispersive, frequency-selective element, and wherein these two frequency-selective elements or one element thereof can be detuned by way of a correction means (10) for harmonization to each other, which is characterized in that the portion of the light reflected from the external resonator with the angle-dispersive, frequency-selective element back to the semiconductor laser diode and not optically coupled into the semiconductor laser diode (designated as “non-optically coupled light”) or part thereof, is measured and that from the relevant measuring values, after comparison with a reference value, a fault signal is generated which as control variable activates the correction means for synchronization of the frequency-selective elements. Furthermore, the invention relates to device for implementing the method.