Mixed “micellar copolymer-nanoparticle” solutions are of great interest mainly because the improvements in properties could be obtained at low volume fractions of polymers or nanoparticles. Concentrated micellar solutions exhibit a temperature-induced fluid-to-crystal phase transition. The addition of nanoparticles triggers the formation of polycrystallized micellar micrograins, above the transition temperature, instead of a cubic monocrystal. This transition is associated with the segregation of nanoparticles, which act as impurities, in the interstices between the grains. The purpose of this presentation is to give an overview of the role played by each component. We will describe the thermo-rheological properties of the solutions studied, depending on the concentration of copolymer and nanoparticles. The viscoelastic behavior and its temperature dependence will be discussed. The rheological properties will be discussed in light of additional information obtained from differential calorimetry and structural studies performed on these systems.