The combined sonochemical/solvothermal syntheses were developed to synthesize nanostructured materials. In this research, the Cd(NO₃)₂·4H₂O and (NH₄)₂S chemicals were dissolved in ethylenediamine, sonicated for 1–5 h under ultrasonic radiation and followed by the solvothermal synthesis at 200 °C for 24 h. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), UV–visible (UV–vis) spectrometry and Raman spectroscopy. The analyses showed pure phase of hexagonal CdS uniform nanorods. To achieve 1–3 μm long and 20–30 nm diameter nanorods, the process was done by the 5 h ultrasonic route combined with the 200 °C and 24 h conventional solvothermal reaction. These nanorods became the mixture of nanoparticles, nanorods and microrods when the solution mixture was processed by only the conventional solvothermal method. In addition, the absorption peak of the long nanorods was detected at 487 nm.