Three new C-methylated acetogenins, (2E,6Z)-9,10-dihydroxy-4-hydroxymethyl-2,6-decadiene (1), (2E,6Z)-8,9,10-trihydroxy-4-hydroxymethyl-2,6-decadiene (2), and (2E,6Z)-9-hydroxy-4-hydroxymethyl-2,6-nonadiene (3), together with two known compounds, p-hydroxybenzyl alcohol (4) and indolyl-3-carboxylic acid (5), were isolated from endophytic fungus S20 of Cephalotaxus hainanensis Li. Their structures were determined based on HR-ESI-MS and spectroscopic techniques (IR, UV, 1D, and 2D NMR). Compound 5 showed inhibitory effects on Staphylococcus aureus and methicillin-resistant S. aureus by the filter paper disc agar diffusion method.