Controlled crystal growth of calcium oxalate was examined under the influence of Gum Arabic (GA) and urea at pH 4.0, 7.0, and 9.0. GA when alone directed the formation of calcium oxalate dihydrate (COD) up to 2.0% w/v concentration, whereas urea influenced the formation of calcium oxalate monohydrate (COM). The combination of urea and GA in mixed proportions (2.0% w/v each) led to the formation of nanocrystallites of COD. The present study on crystallization behavior of calcium oxalate under the influence of natural polysaccharides and urea may prove to be important in understanding the control of kidney stone formation.