The mechanical properties of sintered nanostructured Pb1-xCuxTe (0 ≤ x ≤ 0.2) alloy systems were investigated using nanoindentation technique. The powder precursors of the designed systems were prepared by ball milling technique and sintered by hot isostatic pressing. Cu acts as a dopant in these alloy systems, and an increase in its concentration, up to x = 0.1, leads to a more dense and refined nanostructure along with enhancements in both hardness and Young's modulus. The Cu addition caused an apparent embrittlement in the materials, and spalling of the materials was recognized when x exceeded 0.15. These results imply that design parameters of complex mechanical environments under thermal shocks and vibrations cannot be determined only in terms of hardness and Young's modulus of thermoelectric systems like Pb1-xCuxTe alloys.