Two new sesquiterpenoids, flammupin A (1) and flammupin B (2), along with two known compounds, enokipodin C (3) and 5,5'-dibuthoxy-2,2'-bifuran (4) were obtained from Flammulina velutipes, an endophytic fungus isolated from the roots of Caulophyllum robustum Maxim. The structures were elucidated by the combination of HR-ESI-MS, NMR, and ECD analyses. Compound 3 exhibited moderate to potent cytotoxicity against A549, HeLa, and SMMC-7721 cells with IC50 values ranged from 3.69 to 11.84 μM.