A novel benzofuranone dimer, named incarviditone (1), along with known rengyolone (2), was isolated from Incarvillea delavayiBureau et Franchet. The structure of the new compound was elucidated on the basis of spectroscopic methods, especially 2D-NMR and MS analyses. Compound 1 is the first example of a benzofuranone dimer connected by a CC bond, which presents a new C-skeleton. The cytotoxicities of compounds 1 and 2 were evaluated against the cell lines A549, LOVO, HL-60, 6T-CEM, and HepG2. Incarviditone (1) exhibited cytotoxicity only against HL-60 and 6T-CEM cell lines with IC50 values of 14.8 and 22.2 μg/ml, respectively, while rengyolone (2) was more active against all cell lines with IC50 values between 6.7 and 20.2 μg/ml.