This paper demonstrates sensors based on multi-walled carbon nanotube (MWNT) networks decorated with metal nanoclusters for benzene vapor detection at room temperature. MWNT networks were deposited between the interdigitated metal electrodes on a Si/SiO2 substrate by AC dielectrophoresis. Metal nanoclusters including Au, Pt, Ti and Ni were deposited by magnetron sputtering onto the MWNT networks with a controlled loading of equivalent thickness of 1.5-1.8 nm as the active sensing layer. The resistances of MWNT networks are reduced after functionalized with metal nanoclusters. Experimental results show that resistances of unmodified and metal-functionalized MWNT networks increase after exposing to benzene, ethanol and water vapor. The MWNT networks decorated with Au, Pt and Ti have more sensitivity than bare MWNT networks while Ni decoration did not enhance the sensitivity of MWNT networks to benzene vapor. The MWNT networks decorated with Pt exhibited highest resistance response to benzene vapor, with a less interference of ethanol vapor and humidity.