A process for non-covalent functionalization of multi-walled carbon nanotubes with metal-tetraphenylporphyrins is reported in this paper. The TEM and SEM images and FTIR results show that the nano-sized clusters of aggregated metal-tetraphenyl porphyrin molecules get attached and anchor the surface of carbon nanotubes. We have utilized the prepared nano-composites to fabricate very fast and sensitive sensors for detection of benzene, toluene and xylene in vapor form. The sensors made from cobalt-, and copper-tetraphenylporphyrins functionalized multi-walled carbon nanotubes having resistivity in the kilo-ohms range show response and recovery times of few seconds. However, the response and recovery times and change in resistance are strongly dependent on the type of metal-porphyrin and the chemical vapors. With the help of principal component analysis and other statistical techniques, these sensors can be used in sensor arrays to identify the specific chemicals in vapor form. The nano-composite sensors are easy to fabricate, portable, low cost, reversible, stable and very fast for detection of benzene, toluene and xylene chemicals in the vapor form.