Several natural products have been found to have anti-tumor promoting activity. In the present study, we carried out a primary screening of ten terpenoid coumarins isolated from plants of the Ferula species, examining their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) in Raji cells. Auraptene (7-geranyloxycoumarin, 1) and umbelliprenin (7-farnesyloxycoumarin, 2) were found to significantly inhibit EBV-EA activation and preserved the high viability of Raji cells, suggesting that they might be valuable anti-tumor-promoting agents (IC50 8.3 and 9.1 nM, respectively). Our findings revealed that the presence of a prenyl moiety in the terpenoid coumarins plays an important role in anti-tumor promoting activity as previously reported for xanthones, coumarins, flavonoids and phenylpropanoids.