Using acid-catalyzed degradation in the presence of cysteamine, the condensedtannins from Lithocarpus glaber leaves were characterized, following thiolysis, by meansof reversed-phase HPLC, 13C-NMR and matrix-assisted laser desorption/ionization time offlight mass spectrometry (MALDI-TOF MS) analyses. The thiolysis reaction productsshowed the presence of the procyanidin (PC) and prodelphinidin (PD) structures. The 13CNMRspectrum revealed that the condensed tannins were comprised of PD (72.4%) and PC(27.6%), and with a greater content of cis configuration rather than the trans configurationof C2–C3. The MALDI-TOF MS analysis proved the presence of PD units, and themaximum degree of polymerization (DP) was an undecamer. The antioxidant activity ofcondensed tannins from L. glaber leaves was evaluated by using a free radical scavengingactivity assay.