Vanillin, which is principal aroma constituent of the beans obtained from vanilla orchids, is one of the most demanded flavoring agents in the world. Because of insufficient supply of natural vanillin, market demand is usually supplied by synthetic ones. Taking into consideration of consumer trends, interest to natural products are rising day by day instead of the synthetic counterparts. In this study, it was investigated possibility of usage biphasic system in bioconversion process of isoeugenol to vanillin by Pseudomonas putida (HUT 8100) culture. Organic phase was composed of isoeugenol as sole carbon source in medium while biocatalyst, P. putida culture, was dispersed in inorganic phase. Incubation was performed at 28 ○C, at pH 6.3 and 180 rpm shaking. Isoeugenol and vanillin amounts in medium were simultaneously analyzed in HPLC system at 270 nm. Isoeugenol has low solubility in water and it was tested in concentrations ranged between 5-60% (w/w) to compose biphasic system. In various initial substrate concentrations, vanillin reached the highest level in the medium containing 40% (w/w) isoeugenol after 120 h. In specified conditions, isoeugenol consumption and vanillin production were investigated by following the bioconversion medium periodically for 17 days. According to the obtained results, it was determined that 11.95 g L-1 vanillin was produced with 6.2% molar yield at the end of 15 days bioconversion. It is thought that, obtained result by using biphasic system is very important for the industrial applications in production of natural vanillin via bioconversion.