The elastic moduli of two-phase (γ-matrix and γ'-precipitates) nickel-base alloys show a strong decrease between 1000 and 1100°C. Damping measurements were carried out with specimens of the nickel-base superalloy CMSX-4, a near-γ matrix material, and the intermetallic phase Ni3Al (considered as near γ') with the aim to achieve a better understanding of this elastic moduli decrease. For the determination of the damping a free-free beam technique was applied. In CMSX-4 two different damping peaks separated by about 70 K for each mode of the flexural vibration are found between 1000 and 1200°C. The corresponding relaxation processes cause a modulus defect of about 20%. The damping spectrum of the near-γ' material Ni3Al is very similar to that observed for the alloy, with two relaxation peaks in the same temperature range. In contrast to that, the near-γ matrix material exhibits only one maximum in the spectrum. A comparison of the evaluated damping parameters of the relaxation peaks in the different materials leads to the conclusion that the diffusion of nickel and aluminum atoms in the γ'-phase most probably is responsible for the observed relaxations.