A chemical study of metabolites of the strain Penicillium sp. P-1, an endophyte from the stems of Huperzia serrata, furnished a new chromone derivative, (2S)-2,3-dihydro-7-hydroxy-6,8-dimethyl-2-[(E)-prop-1-enyl]chroman-4-one (1), an enantiomer of a known compound, and seven known compounds 2–8. The structure and absolute configuration of 1 were established using spectroscopic methods, including extensive 2D NMR and CD analyses. Cytotoxic activity of compounds 1–3 against HeLa and HepG2 cell lines were evaluated, in which compounds 2 and 3 exhibited marked cytotoxic activity against HeLa cells.