The purpose of this study was to determine anticholinesterase activity of essential oils and extracts from Thai indiginous plants. The antioxidant of plant extracts was also examined. The anticholinesterase activity of 13 essential oils from Thai medicinal plants was primarily evaluated using purified AChE from eel. Results revealed only essential oils from turmeric, galangal and fingerroot exhibited the appreciable effects. Tturmeric oil had strongest activity while galangal oil showed higher activity than fingerroot oil. Their constituents were then identified and also investigated for AChE inhibitory activity. Results revealed a number of constituents were found but their effect on AChE was not strong as their originated oils either in single or combination. When turmeric, galangal and fingerroot oils were tested in neuroblastoma SK-N-SH cells, they showed the appreciable potentials in inhibiting cellular AChE of these cells as well. The anticholinesterase and antioxidant activity of 66 plants extracts were investigated by using purified AChE from eel and cellular enzyme . The result showed that the extract from Glochidion hypoleucum, Eugenia grata/Syzygium gratum and Schinus Terebinthifolius Raddi demonstrated strong anticholinesterase activity. The antioxidant activity of the plant extracts was evaluated by DPPH and FRAP assay. The extract from Caesalpinia mimosoides Lamk., Schinus Terebinthifolius Raddi and Glochidion hypoleucum showed potent antioxidant activity. Among the active compound of these extracts, gallic acid, ursolic acid, quercetin and kaempferol showed strong anticholinesterase activity while ethyl gallate, quercetin, methyl gallate, gallic acid and kaempferol demonstrated impressive antioxidant activity. Thus, gallic acid, quercetin and kaempferol, showed both anticholinesterase and antioxidant activity. The present study revealed that turmeric, galangal and fingerroot oils are interesting essential oil in terms of AChE inhibitory effect. In addition, the active compound from the extracts of Glochidion hypoleucum, Schinus Terebinthifolius Raddi, Eugenia grata/Syzygium gratum, and Caesalpinia mimosoides Lamk. were impressive in the AChE inhibitory and antioxidant effect. These oils and extracts may be the good candidates to be used in either form as the functional ingredients for AD patients. Avoidably, a number of biological and toxicological studies as well as the study on product development have to be done, especially in animal model and in human subjects, to confirm and support their efficacy with safety before being able to promote the use for prevention and treatment of Alzheimer’s disease. Furthermore, gallic acid, quercetin and kaepferol may be used as the lead compound for these activities.