Values of the nonlinearity constantDwhich determines the coupling of acoustic phonons with the thermal phonons have been evaluated for the semiconducting material germanium in the temperature range 297–78.9 °K using the experimental data of second‐ and third‐order elastic constants of this material. The temperature‐dependent behavior of this constant has thus been tested for the first time on a theoretical basis through ultrasonic attenuation evaluated for high‐frequency compressional waves, propagating along the ⟨100⟩ direction in single‐crystal germanium. The results obtained are found to be in excellent agreement with the experimental values observed previously.