Ten β-carboline alkaloids, including five new and two new naturally occurring compounds, sphecolines A–G (1–7), together with four known isocoumarins were isolated from a wasp-pathogenic fungus Ophiocordyceps sphecocephala BCC 2661. Structures of these compounds were determined by NMR spectroscopic and MS spectrometric analyses. Sphecolines A (1) and C (3) exhibited cytotoxic activity against human small-cell lung cancer NCI-H187 cell lines, with IC50 values of 79.9 and 75.1 μM, respectively.