In view of the ever-growing importance of ion beams in optical material processing, this letter reports room-temperature MeV He+ ion irradiation induced depletion of hydrogen from single crystalline potassium dihydrogen phosphate (KH2PO4 or KDP) which has wide applications as a nonlinear optical material in optoelectronics technology. Irradiations have been performed using 1.5 MeV He+ ions up to a maximum dose of 2.4 × 1015 ions/cm2. Simultaneously, hydrogen profiling has been done by detecting the elastically recoiled H atoms. Bare KDP crystals show a hydrogen loss of 72% at the maximum dose whereas Au coated samples show that 60 Å of Au layer acts as a barrier to considerably reduce hydrogen depletion from KDP. A possible explanation of these phenomena is suggested.