<p>The stems of <i>Rhododendron mucronulatum</i> for. <i>albiflorum</i> (SRMA), particularly its ethyl acetate (EtOAc) fraction, have received significant attention due to its medicinal and possible antioxidant effects. This study investigated the potential antioxidant activity of SRMA and analyzed which fraction of the said extract contained the highest phytochemical compounds. The EtOAc fraction showed the highest antioxidant potential, which was further analyzed using LC-MS/MS, five compounds were identified in the EtOAc fraction: taxifolin, myricitrin, hyperoside, quercetin, and kaempferol. The EtOAc fraction exhibited the highest antioxidant activity in the DPPH and ABTS assays among the tested fractions. The antioxidant activity of the five compounds was evaluated using the DPPH and ABTS radical scavenging assays, with all having an IC₅₀ value of 2.5 µmol·mL^-1 or less. The five compounds were quantified using HPLC. The EtOAc fraction was found to contain 77.15 mg·g^-1 of taxifolin, 14.61 mg·g^-1 of myricitrin, 6.60 mg·g^-1 of quercetin, 3.53 mg·g^-1 of hyperoside, and 0.75 mg·g^-1 of kaempferol. The findings show that the high content of five compounds in SRMA extract contributes to its excellent antioxidant activity. Additionally, the EtOAc fraction of SRMA could be a promising source of natural antioxidants for the pharmaceutical and nutraceutical industries.</p>