The nematicidal activity of Kaempferia galanga rhizome-derived materials (methanol extract, steam distillate, and powder) toward M. incognita second-stage juveniles (J2) was examined using residual contact toxicity and pot bioassays. In residual contact toxicity bioassays with J2, the active principles of K. galanga rhizome were identified as the phenylpropanoids ethyl cinnamate (EC, 1) and ethyl-p-methoxycinnamate (EMC, 2) by spectroscopic analysis. EC exhibited 95% and 49% mortality at 0.06 and 0.04 mg/ml toward J2, respectively, whereas EMC showed 98% and 63% mortality at 0.1 and 0.08 mg/ml. In pot tests with J2, K. galanga rhizome methanol extract gave 92% and 82% mortality at 100 and 20 mg/50g soil, respectively. Steam distillate gave 88% and 68% mortality at 85 and 42.5 mg/50g soil, respectively, whereas rhizome powder provided 83% and 62% mortality at 400 and 200 mg/50g soil. K. galanga rhizome-derived materials, particularly EC and EMC, merit further study as potential root-knot nematode control agents or leads because of their great activity as a nematicide.