:In this study, a series of near-infrared (NIR) KZnF3:Cr3+ phosphors was prepared by different chromium sources using a HF-free hydrothermal method. The influence of different chromium sources on the crystal structure, morphology, and luminescence properties of Cr3+-doped KZnF3 phosphors were systematically investigated. The results showed that the chromium source changed from CrF3·xH2O to (NH4)3CrF6 and leaded to an increased crystal field, resulting in a blue shift of the emission peak position from 803 nm to 753 nm, accompanied by the full-width half maximum (FWHM) reduced from 140 nm to 122 nm. Moreover, KZnF3:0.03Cr3+ (CrF3·xH2O) and KZnF3:0.03Cr3+ ((NH4)3CrF6) phosphors maintained 58% and 87% of their initial room-temperature intensity at 423 K, respectively. These results indicated that altering the synthetic raw materials provided new insights for designing NIR phosphors with highly thermal stability.