The emergence of drug resistance and spread of new infectious diseases necessitated the development of novel antibiotics. Marine sponge-associated fungi represent a reservoir of novel molecules with diverse biological potentials. In this study, we isolated five nitrobenzoyloxy-substituted sesquiterpenes 1-5 from the culture mycelia of an endozoic fungus Aspergillus insulicola MD10-2, obtained from the South China Sea sponge Cinachyrella australiensis. Compound 2 showed cytotoxicity against human lung cancer cell line H-460 with an IC50 value of 6.9 µM. Cytotoxicity of the acetylated derivatives (2a and 2b) of compound 2 decreased markedly, suggesting that the hydroxyl group contributed to the cytotoxic activity. Compound 5 was inactive against H-460, which implied the double bond at C-7 had an effect on cytotoxic activity as well.