Three known isoquinoline alkaloids were isolated from the chloroform-soluble fraction of the methanolic extract of the aerial parts of Corydalis incisa (Papaveraceae) through repeated column chromatography. Their chemical structures were elucidated as corynoline (1), corynoloxine (2) and 6-oxocorynoline (3) using spectroscopic analysis. Compounds 1-3 exhibited cytotoxicity against human A549, SK-OV-3, SK-MEL-2 and HCT15 tumor cells.