A new hydrogen sensor utilizing plasma-enhanced chemical vapor deposited diamond in conjunction with palladium (Pd) metal has been developed. The device is fabricated in a layered Pd/undoped diamond/p-doped diamond Schottky diode configuration. Hydrogen sensing characteristics of the device have been examined in terms of sensitivity, linearity, response rate, and response time as a function of temperature and hydrogen partial pressure. Hydrogen adsorption activation energy is investigated in the temperature range from 27 to 85-degrees-C. Analysis of the steady-state reaction kinetics using the I-V method confirm that the hydrogen adsorption process is responsible for the barrier height change in the diamond Schottky diode. The ability to fabricate diamond-based hydrogen sensor on a variety of substrates makes the device very versatile for gas sensing.