This investigation examined methanolic extracts derived from leaves and branches of three bamboo species, namely Dendrocalamus sericeus Munro, Dendrocalamus asper (Schult. & Schult.f.) Backer and Bambusa nutans Wall. ex Munro, to evaluating total phenolic content (TPC) and antioxidant capacity by 2,2-diphenyl-1-picrylhydrazine (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) assays, while phenolic compounds were identified by high-performance liquid chromatography coupled with photodiode array detection (HPLC-PDA). The highest TPC was observed in D. asper branch extracts (0.143 ± 0.005 mg GAE/g sample). However, leaf extracts showed stronger antioxidant activity. Bambusa nutans leaf extracts exhibited the lowest DPPH IC50 (0.162 ± 0.007 g/mL),
while D. asper leaf extracts showed the highest ABTS activity (IC50 = 0.029 ± 0.002 g/mL). The greatest reducing power was found in D. sericeus leaf extracts (FRAP = 23.333 ± 0.196 μmol TE/g sample). high-performance liquid chromatography coupled with photodiode array detection analysis identified nine phenolic compounds, with chlorogenic acid predominating in D. asper branch extracts. In contrast, leaf extracts contained higher levels of flavonoids and low-molecular-weight phenolic acids, including epicatechin, p-coumaric acid and vanillic acid. These compositional differences explain the stronger antioxidant activity of leaf extracts despite their lower TPC. Overall, antioxidant capacity was more strongly influenced by phenolic composition than by TPC. These data provide a scientific basis for the strategic utilisation of bamboo species and plant parts in nutraceuticals, functional foods and related fields.