This work investigates the influence of iron doping on Potassium Hydrogen Phthalate (KHP) single crystals by the slow evaporation solution growth technique. Factors such as evaporation rate, solution pH, solute concentration, super saturation limit, etc. are very important in order to have optically transparent single crystals. As part of the work, the effects of metallic salt FeCl3 in different concentrations were analyzed with pure KHP. Powder X-ray diffraction suggests that the grown crystals are crystallized in the orthorhombic structure. The functional groups and the effect of moisture on the doped crystals can be analyzed with the help of a FTIR spectrum. The pure and doped KHP single crystal shows good transparency in the entire visible region, which is suitable for optical device applications. The refractive indices along b axis of pure and doped KHP single crystals were analyzed by the prism coupling technique. The emission of green light with the use of a Nd:YAG laser (λ=1064 nm) confirmed the second harmonic generation properties of the grown crystals. © 2010 Elsevier B.V. All rights reserved.