Cassia fistula is widely distributed in Vietnam; however, studies on the botany, chemical composition, and biological activities of its flowers remain limited. This study aimed to investigate the botanical characteristics, conduct a preliminary phytochemical screening, and evaluate the antioxidant and α-glucosidase inhibitory activities of C. fistula flowers. Microscopic anatomical features were observed using a double-staining method. Preliminary phytochemical screening was carried out using a modified Cuiley method. Total polyphenol content was quantified using the Folin–Ciocalteu reagent and UV-Vis spectrophotometry. Antioxidant activity was evaluated based on DPPH free radical scavenging assay, while 
α-glucosidase inhibitory activity was assessed according to the method of Hua Qiang Dong (2012).The results revealed that C. fistula possesses characteristic botanical and chemical features of the genus Cassia, family Caesalpinioideae. The polyphenol content decreased in the order: FICF70 (26,29 ± 0,07 mg GAE/g dry material), FICF50 (24,02 ± 0,10 mg GAE/g dry material), FICF00 (23,63 ± 0,26 mg GAE/g dry material), and FICF96 (11,10 ± 0,25 mg GAE/g dry material). The DPPH assay showed that antioxidant activity followed the same decreasing order: FICF70 > FICF50 > FICF00 > FICF96. All extracts demonstrated significant α-glucosidase inhibitory activity, with FICF96, FICF70, and FICF50 showing similar IC₅₀ values, all lower than that of the aqueous extract. These findings provide additional scientific data on C. fistula flowers and contribute to enhancing the therapeutic potential of Vietnamese medicinal plants.