This paper discusses the in vitro antimicrobial activity and fungitoxicity of syringic acid, caffeic acid and4-hydroxybenzoic acid which is found in oil palm root. Experiments were observed for fourteen days, repeated at leastthree times and data were recorded daily. The antimicrobial activities and fungitoxicity of the phenolics againstGanoderma boninense were expressed in inhibition of radial growth of G. boninense on PDA ameliorated with the threedifferent phenolics with a range concentration of 0.5-2.5 mg/ml. Syringic acid was found to be very fungitoxic to G.boninense even at concentration of 0.5 mg/ml, the lowest concentration tested in this experiment. When theconcentration is increase to 1.0mg/ml of syringic acid, the pathogen is inhibited. Caffeic acid and 4-hydroxybenzoicacid were having inhibitory effect with the highest concentration tested; 2.5mg/ml strongly inhibited the growth of G.boninense in comparison to the control.