A systematic study on the microwave-assisted thermolysis of the single source precursor (Et₂Sb)₂Te (1) in different asymmetric 1-alkyl-3-methylimidazolium- and symmetric 1,3-dialkylimidazolium-based ionic liquids (ILs) reveals the distinctive role of both the anion and the cation in tuning the morphology and microstructure of the resulting Sb₂Te₃ nanoparticles as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). A comparison of the electrical and thermal conductivities as well as the Seebeck coefficient of the Sb₂Te₃ nanoparticles obtained from different ILs reveals the strong influence of the specific IL, from which C₄mimI was identified as the best solvent, on the thermoelectric properties of as-prepared nanosized Sb₂Te₃. This work provides design guidelines for ILs, which allow the synthesis of nanostructured thermoelectrics with improved performances.