A mechanical spectroscopy study has been made on fine-grained Ni-10vol%TZP(ZrO2-3mol.%Y2O3) composite in an attempt to assess the following micromechanical prediction. A dual-phase material with fine-grained constituents deforming by Coble-type boundary-diffusion creep exhibits viscoelastic behavior. Dynamic Young's modulus and internal friction are measured over a temperature range of 25 to 800oC at frequencies of 0.01, 0.05 and 0.1Hz using a specially designed tension-compression apparatus. Two relaxation peaks are observed in the composite. An exponential involved in the peak and background components are determined and, by making a further analysis based on the micromechanical formulation and also taking the well-known relaxation due to viscous grain-boundary sliding into account, the implications of these quantities are discussed in terms of constituent material parameters(boundary diffusivity, grain size, etc.).