In this paper optically stimulated luminescence (OSL) properties of Pr3+-doped double potassium yttrium fluoride (K2YF5) under green light stimulation at room temperature as a function of the doping concentration are reported. Besides, some characteristics concerning the possible application of this composition as a new OSL dosimeter are presented, namely, the dose–response and fading of the OSL signal. The residual thermoluminescence (TL) response of K2YF5:Pr3+ after the OSL experiment has been investigated in order to establish whether the traps responsible for OSL are also involved in the TL process. Spectral analysis of the OSL emission has been carried out to determine the role played by Pr3+ ions in the radiative relaxation process. Finally, the total OSL output of K2YF5:Pr3+ is compared to that of commercial Al2O3:C.