CrSi2 alloy presents a strong interest for thermoelectric applications; however, its thermal conductivity is still too high and limits strongly its figure of merit. By combining experiment and modeling, we show that the nanostructuring of CrSi2 leads to a strong decrease in the thermal conductivity without affecting much the electronic transport properties. The thermal conductivity of nanostructured CrSi2 (∼45 nm) has also been determined as a function of the density. We predict that it would be about 5.5 W/mK at RT for a 100% dense sample, i.e., twice smaller than in bulk samples. We also give for the first time, a prediction of the effect of alloying on the thermal conductivity using the Callaway-Klemens model. To consider final applications, it is necessary to also investigate the thermal stability of nanostructured compounds. We show that grain coarsening of nanostructured CrSi2, even if it remains limited, happens above 1073 K and will deserve further attention.