A polydimethylsiloxane (PDMS)-coated nanoelectromechanical systems diaphragm embedded with silicon nanowires (SiNWs) is proposed for chloroform vapor detection at room temperature. The PDMS film swells and leads to the deformation of micro-diaphragm when it is exposed to vapor. The SiNWs are connected in a Wheatstone bridge which is used to transform the deformation into a measurable output voltage. This sensor provides good linearity, sensitivity, and repeatability. The sensitivity of our sensor for chloroform vapor detection is 1.41 μV/V/ppm, while the power consumption is as low as 2 μW.