Versicolactones A–D (1–4), four new butyrolactones, along with four known butyrolactones (5–8) were isolated from the fermentation products of the endophytic fungus Aspergillus versicolor. The structures of compounds 1–4, including absolute configuration, were elucidated by interpretation of the NMR and CD data. Compound 2 was further confirmed by single-crystal X-ray diffraction analysis. In particular, compound 1 is the first naturally occurring butyrolactone possessing an unusual 2-oxopropyl group. More importantly, compounds 1 and 8 displayed significant antitobacco mosaic virus activities with inhibition rates of 46.4 % and 35.4 %, even more potent than the positive control ningnanmycin (30.8 %). Compound 1 also showed moderate cytotoxicity against A549 and MCF7 cells with IC₅₀ values of 3.2 and 2.5 µM, respectively.