Abstract: Background and Objective: Microbial accumulation in oil industry's pipeline system would eventually leads to biofilm formation, which could initiate biocorrosion. Biofilm-biocorrosion caused great loss in industry and is essential to be included in mitigation program. Essential oils extracted from plants are known to have anti-microbial properties. This study aimed to further investigate the effect of lemongrass (Cymbopogon citratus) essential oil in emulsion and microemulsion form against biofilm in formation water environment. Materials and Methods: Thermodynamic stability of microemulsion was observed with centrifugation, heating-cooling cycle and freeze-thaw cycle method and confirmed with particle size measurement. Results: Lemongrass essential oil treatment was able to prevent both biofilm and planktonic bacterial growth and eradicate biofilm. Minimum inhibitory concentration (MIC) of emulsion was observed at essential oil concentration of 0.06% (v/v). The minimum biofilm inhibitory concentration of emulsion and microemulsion assayed on carbon steel were 0.06 and 0.03%, respectively. Minimum biofilm eradicating concentration of emulsion and microemulsion were both 1% with eradication percentage of 53.03 and 88.39%, respectively. Biocorrosion mitigation potential of lemongrass essential oil was most effective (96.786% inhibition) at 2% (v/v) after 6 h of exposure. Conclusion: Essential oil in emulsion and microemulsion form could perform as alternative to chemical biocide in mitigating biofilm-biocorrosion.