Dimethyl methylphosphonate (DMMP) is widely used as a simulant of nerve agent Sarin, which is an organophosphorus compound. In the present work, flexible single walled carbon nanotube (SWCNT) resistive sensor is functionalized with 4-(Hexafluoro-2-hydroxy isopropyl)aniline (HFiP-1) to enhance the response of the sensor towards DMMP vapors. Sensing properties of pristine and HFiP-1 functionalized flexible SWCNT resistive sensors for DMMP vapors are investigated at room temperature. The response of HFiP-1 functionalized sensor is enhanced towards DMMP due to the presence of strong hydrogen-bonding between the organophosphonate and HFiP-1. The response of functionalized sensor is 16.0% for 24 ppm of DMMP and increased 3.7 folds as compared to pristine sensor. The observed results indicate that, HFiP-1 plays a significant role in enhancement of SWCNT film sensor response towards DMMP. In addition, the flexible sensor fabricated by vacuum filtration method and functionalized using drop cast method gives repeatable response over five cycles that have been studied. (C) 2016 Elsevier B.V. All rights reserved.