Five spirobisnaphthalenes, namely palmarumycin CP17 (1), diepoxin kappa (2), diepoxin eta (3), diepoxin xi (4), and diepoxin gamma (5), were isolated from the endophytic fungus Dzf12 associated with the medicinal plant Dioscorea zingiberensis C. H. Wright. Their structures were identified by physicochemical and spectrometric analysis. Among these spirobisnaphthalenes, 2 was found to have antibacterial activity, and the mixture of 3 and 4 was detected to have both antibacterial and antifungal activities.