Modified diamond nanoparticles (DNP) are investigated as sensitive coatings for use with Surface Acoustic Wave (SAW) transducers. DNP were surface treated (e.g. hydroxylation, hydrogenation) to enhance their affinity to specific compounds such as nitro-aromatic compounds, nerve-agent stimulant, or toxic gases. They were deposited onto SAW transducers by a layer-bylayer deposition method to assess their performances for chemical vapor sensing. The DNP coated sensors were tested towards dinitrotoluene (DNT), dimethylmethylphosphonate (DMMP), ammonia (NH3) and relative humidity (RH). The sensors showed high sensitivity to the target compounds, good repeatability and low detection limit at sub-ppm levels, at room temperature.