In this work, CdS nanoparticles were synthesized via chemical method using thioacetamide (TA). X- ray diffraction (XRD), Atomic force microscopy (AFM) and UV-VIS transmission spectroscopy were employed to characterize the size, morphology, crystalline structure and optical properties of the prepared material. X-ray diffraction analysis confirms the formation of cubical and hexagonal structures of CdS nanoparticle with average particle size (3.2nm). AFM show the formation of aggregate of nanoparticle with particle size ranging 7 – 20 (nm). From the shift in optical band gap, particles size can be calculated using Effective mass approximation (EMA) was (2.3nm), and found a good agreement with those determined from XRD broadening, while AFM show higher particle size due to aggregation of nanoparticles.