For high sensitive and multiplexed chemical analysis, an opto-mechanical detection platform has been built. To check the performance of the platform, we performed water vapor response measurements for the cantilevers coated with alkane thiols having different functional end groups. Furthermore, for the exposure of 50 ppb toluene vapor to carboxylic benzene thiol coating layer, nanoscale static deflection of the cantilever sensors has been measured simultaneously. The nanomechanical platform using cantilever sensors can be miniaturized to be used for high sensitive and selective environmental monitoring for indoor or outdoor air pollutants, mold, heavy metals, and other health hazard materials.