Light yield (LY) and its ratio under excitation with α- and γ- rays (α/ γ ratio) were measured for Y3Al5O12:Pr (YAG:Pr) single crystals with Pr concentration of 0.16, 0.33 and 0.65 wt%. YAG:Pr (0.33 wt%) showed a highest LY value of 14,900 ph/MeV at 662 keV γ- rays, while a highest LY value of 3,700 ph/MeV at 5.499 MeV α- particles was measured for YAG:Pr (0.65 wt%) one, showing a highest α/ γ ratio of 0.26. A clear separation was observed for 5.155, 5.486 and 5.806 MeV α- particles from a mixed tri-nuclides alpha source. Light yield dependence on sample height was measured under excitation with α - rays and the light loss coefficient was estimated and compared to the value measured for the LuAG:Pr sample with comparable size and Pr concentration.