Background: Medicinal plants play an important role in the alternative or complement therapy to manage of urinary stones at this time. Terminalia genus was proved anti-urolithiatic activity via in vitro inhibition of calcium oxalate formation. Among the samples, Terminalia catappa showed as a potential plants for this activity in India. Moreover, they were a common plant species in Vietnam and there was no research on this topic in our country. Objectives: To evaluate in vitro anti-urolithiatic activity of Terminalia catappa leaves in Vietnam, through inhibition of calcium oxalate formation. In addition, moisture value, preliminary screening of the chemical composition and determination of tanninoid content of aqueous extract also were conducted. Materials and methods: Moisture content of herbs was conducted according to guidelines of 5th Vietnam pharmacopoeia, appendix 9.6. Qualitation of the phytochemical constituents of aqueous extract with appropriate reagents to confirm the presence of natural compounds via chemical reactions. Determination of tanninoid content of aqueous extract was evaluated by using oxidation-reduction titration method (Lowenthal assay) and skin powder method in instructing of appendix 12.6 from 5th Vietnam pharmacopoeia. Inhibitory effect of calcium oxalate formation of three hydrophilic extracts (45% ethanol, 96% ethanol and aqueous extracts) was confirmed by nucleation assay with cystone as a positive control. Results: Moisture content of medicinal plant was 11.625%. Terminalia catappa leaves contain the major phytochemical constituents such as flavonoids, tanninoids and saponins. The tanninoid content according to Lowenthal method and skin powder method were 10.88% and 10.70%, respectively. Therefore, the average tannin content was confirmed to be approximately 10.79%. Among the investigated samples, aqueous extract showed the best inhibitory activity of calcium oxalate crystal formation with an IC₅₀ of  602.67 μg/mL when compared to cystone with IC₅₀ 423.05 μg/mL. Conclusions: The aqueous extract from Terminalia catappa leaves has been shown to be a promising source for anti-calcium oxalate crystals formation activity on experimental model. The anti-urolithic potential of Terminalia catappa leaves may be related to its major phytoconstituents.