Four new depsidones, mollicellins O–R (compounds 1–4), along with three known compounds 5–7, were isolated from cultures of the fungus Chaetomium sp. Eef-10, an endophyte isolated from Eucalyptus exserta. The structures of the new compounds were elucidated by analysis of the 1D and 2D NMR and HR-ESI-MS spectra. The known compounds were identified by comparison of their spectral data with published values. Compounds 1–7 were evaluated for antibacterial activities against Staphylococcus aureus (sensitive and resistant strains), Escherichia coli, Agrobacterium tumefaciens, Salmonella typhimurium, Pseudomonas lachrymans, Ralstonia solanacearum, Xanthomonas vesicatoria and cytotoxic activities against two human cancer cell lines (HepG2 and Hela). Mollicellin H (6) displayed best antibacterial activity, with IC₅₀ values of 5.14 µg/mL against S. aureus ATCC29213 and 6.21 µg/mL against S. aureus N50, MRSA, respectively. Mollicellin O (1) and mollicellin I (7) also exhibited antibacterial activities against S. aureus ATCC29213 and S. aureus N50. Mollicellin G (5) was active against both two human cancer cell lines, with IC₅₀ values of 19.64 and 13.97 µg/mL while compounds 6 and 7 only showed cytotoxic activity against one cell line. In addition, mollicellin O (1) showed antioxidant activity based on DPPH radical scavenging, with an IC₅₀ value of 71.92 µg/mL.