Abstract: As one of the most productive species,Trichoderma asperellum,especially isolated from marine algae,has contributed a number of new terpenes and nitrogen-bearing compounds,encouraging our continuous efforts to further explore them. Consequently,three new nitrogen-containing secondary metabolites,including cyclo(L-5-MeO-Pro-L-5-MeO-Pro) (1),5′-acetoxy- deoxycyclonerin B (2),and 5′-acetoxy-deoxycyclonerin D (3) were isolated from the marine alga-derived endophytic fungus Trichoderma asperellum A-YMD-9-2. Their structures and relative configurations were fully elucidated through spectroscopic techniques,mainly including 1D/2D NMR and MS. The absolute configurations of 1 and 2 were ascertained on the basis of X-ray diffraction (Cu Kα radiation) and ECD data,respectively. The isolation of these new nitrogen-bearing compounds adds to the structural diversity of marine algicolous Trichoderma spp.,and they display potent inhibition against some marine phytoplankton species.