AbstractFrom the acetone extract of fresh‐betel nuts, two procyanidin pentamers, two procyanidin tetramers and three procyanidin trimers, along with (+)‐catechin, (‐)‐epicatechin, procyanidin A‐l, procyanidin B‐l, procyanidin B‐2, and procyanidin B‐7 were isolated. Based on 1H NMR and 13C NMR spectral data as well as the results of thiolysis degradation, the chemical structures of two series of oligomeric arecatannins A and B have been established. The arecatannins from betel nuts were found to be condensed‐type tannins which possess (‐)‐epicatechin unit and (+)‐catechin units. All arecatannins had C4‐C8 linked (‐)‐epicatechin in the upper units whereas the (+)‐catechin in the terminal unit had C4‐C8 or C4‐C6 linkage.