We prepared Eu 3+ - and Sm 3+ -doped YNbO 4 phosphor powders using a simple solid-state reaction method and examined their photoluminescence properties in order to investigate the possibility for their usage in phosphor thermometry. Photoluminescence measurements were performed in the temperature range 303–773K, and the fluorescence intensity ratio of the paired emissions lines was studied as a function of temperature. The results have shown that YNbO 4 :Eu 3+ possesses the absolute sensitivity of approximately 3×10 −3 K −1 at about 700K, while relative sensitivity changes within the range of 0.5–2.7%K −1 . YNbO 4 :Sm 3+ has the maximum sensitivity of around 7×10 −4 K −1 at about 700K with the relative sensitivity of 0.43%K −1 around 500K. Calculated temperature sensitivities of samples show that these materials have a good potential for the development of thermographic phosphors. Experimental lifetime measurements recorded at 303–773K were fitted using a temperature dependent charge transfer model, TDCT. This model yields good agreement between experimental and fitted lifetime data. The sample crystalline structure is confirmed by XRD measurements.