We deal with the effect of particle size and concentration on the intensity of turbulent fluctuations in two-phase flows. An interaction between polydisperse particles and the turbulence of the carrier fluid is considered. The theoretical analysis of that process is based on Prandtl’s mixing-length theory, modified to account for the peculiarities of the viscous interaction of small particles and carrier fluid as well as an effect of the admixture inertia. For a particle-laden flow with a bidisperse particle-size distribution, the intensity of turbulent fluctuations of the particles and fluid is determined as a function of the particles sizes and their mass contents. It is shown that at a fixed total mass content of the admixture, the turbulence intensity in polydisperse flow is essentially different from that in monodisperse flow. Some results on the turbulence properties of a turbulent particle-laden jet with a polydisperse admixture are obtained.