Urease was isolated from the seeds of watermelon (Citrullus vulgaris). The optimum temperature and pH was found to be 50° C and 8.3 respectively. Urease shows no loss in their activity when treated overnight with assay buffer of different pH. Watermelon urease thermal inactivation studies revealed a variation in kinetic pattern at different temperatures. At temperature of 50° C and 60° C, urease shows almost no loss in activity i.e. their stable nature. Thermal inactivation (time dependent) shows biphasic kinetics at 70° C, 80° C and 85° C. Investigation studies strongly support the oligomeric nature of the enzyme. The Km and Vmax of Citrullus vulgaris urease was found to be 10 mM and 142.85 µmole of urea/min/mg of protein. The plot of percent residual activity versus the number of days gave a t1/2 of 70 days for urease stored at 4° C and 16 days for urease that stored at 37° C. The I50 values for Hg2+ and NaCl was found to be 6.9 nM and 240 mM respectively, which shows strong inhibitory nature of Hg2+.