The current study attempts to utilize crude urease extracted from watermelon seeds along with urea and calcium source, for the treatment of recycled concrete aggregates. The experimental program involved extraction of urease in a phosphate-EDTA buffer to ensure the stability of the active sites of the enzyme. Its activity was assessed using spectrophotometric method. Subsequently, varying concentrations of this crude urease extract were used to treat recycled concrete aggregates at different temperatures. The results indicated a significant reduction in water absorption for the treated aggregates compared to untreated ones. Furthermore, image analysis of scanning electron images revealed a notable decrease in total porosities of the treated recycled aggregates compared to their untreated counterparts. X-ray diffraction analysis confirmed the presence of calcite, vaterite and aragonite polymorphs of calcium carbonate in the precipitates produced by the activity of the urease enzyme.