This study investigates the adsorption of diclofenac (DCF) onto an olive leaf-derived adsorbent. The harvested olive leaves were washed, dried, and powdered then extracted with 80% ethanol. The extraction was filtered, washed with sodium hypochlorite, and ethanol, and then dried. The material was then activated using sodium hydroxide, phosphoric acid, and dead sea water, for the adsorption of DCF from contaminated water being investigated. Various operational parameters such as dosage, contact time, DCF concentration, and pH were systematically varied to understand their influence on adsorption efficiency. The kinetics of DCF adsorption followed pseudo-second-order kinetics. Isothermal studies revealed that the adsorption process conforms well with the Freundlich isotherm, suggesting multilayer adsorption onto a heterogeneous surface. Thermodynamic analysis indicated that the adsorption process is spontaneous and exothermic. Morphological analysis completed using the SEM data demonstrated a transformation in the porous structure of the adsorbent, indicating effective pore occupation by DCF molecules post-adsorption. Overall, the results demonstrate the effectiveness of olive leaf-derived adsorbent in efficiently removing DCF from aqueous solutions.