Detailed phytochemical investigation from the leaves of Erythrophleum fordii resulted in the isolation of 13 compounds, including three cassaine diterpenoid–diterpenoid amide dimers (1, 3 and 5), and seven cassaine diterpenoid amides (6 and 8–13), together with three previously reported ones, erythrophlesins D (2), C (4) and 3b-hydroxynorerythrosuamide (7). Compounds 1, 3 and 5 are further additions to the small group of cassaine diterpenoid dimers represented by erythrophlesins A–D. Their structures were determined by analysis of extensive one- and two-dimensional NMR experiments and ESIMS methods. Cytotoxic activities of the isolated compounds were tested against HCT-8, Bel-7402, BGC-823, A549 and A2780 human cancer cell lines in the MTT test. Results showed that compounds 1 and 3–5 exhibited significantly selective cytotoxic activities (IC50 < 10 lM) against these cells, respectively.