Objectives : To evaluate the radical scavenging and acetylcholinesterase (AChE) inhibitory activities of the ethylacetate (EtOAc)-soluble portion of a methanolic extract of Aster yomena, three different assay systems were performed. Methods : The antioxidant activity of A. yomena extract was tested as its capacity to scavenging free radicals of DPPH and $ABTS^+$, which has been widely used to evaluate the antioxidant activity of natural products from plant sources. AChE inhibitory activity was tested against mouse brain AChE by spectrophotometric method of Ellman using ELISA microplate reader. Results : The methanolic extract of A. yomena was fractionated and the EtOAc-soluble portion showed significant AChE inhibitory and free radical scavenging effects. Also the EtOAc-soluble portion revealed the highest phenolic contents as compared to the other extracts. Conclusions : These results indicate that phenolic compounds may be important constituents that give rise to the anti-AChE and antioxidative activities of A. yomena extract. Further phytochemical studies on this plant, for nutraceutical or pharmaceutical application, are warranted.