Pharmaceutical compounds in wastewater are a concerning issue. Pharmaceutical wastes cause harmful effects even at low concentrations. This thesis is to investigate the degradation of the pharmaceutical wastes by the photocatalysis process using silver nanoparticles (Ag NPs) decorated zinc oxide (ZnO) nanorods. ZnO nanorods were first synthesized on glass substrate by microwave hydrothermal method. Silver nanoparticles were subsequently deposited on ZnO nanorods by photodeposition technique. Different concentrations of silver nitrate were used and optimized. In addition, effect of annealing temperatures and environments upon silver nanoparticles formation on ZnO NRs were investigated. The synthesized Ag-ZnO nanostructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDXA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible absorption spectroscopy (UV-Vis), and photoluminescence (PL) spectroscopy. XRD, FE-SEM and TEM results confirm that ZnO nanorods have hexagonal wurtzite crystal structure with Ag nanoparticles were successfully attached on ZnO nanorods. XPS results confirm the presence of metallic silver in Ag-ZnO nanostructures. PL results provide an effective separation of photogenerated electron-hole pairs in the Ag-ZnO nanostructures when compared to the pristine ZnO nanorods. UV-visible absorption spectroscopy shows enhance optical absorption in the visible region due to the surface plasmon resonance properties of Ag nanoparticles. The Ag-ZnO nanostructures were used as catalysts for the photodegradation of pharmaceutical compounds (paracetamol and amoxicillin). The photocatalysis results exhibit Ag-ZnO nanostructures have higher degradation than pristine ZnO nanorods where Ag-ZnO catalysts degrade 92 % of 5 ppm paracetamol than ZnO (47% degradation) under visible light irradiation. For 10 ppm amoxicillin, around 67% of degradation using Ag-ZnO catalysts and about 46 using ZnO catalysts.