Oxyfluoride transparent glass‐ceramics (GC) containing CaF2 and ZnAl2O4 nanocrystals have been fabricated with melt‐quenching method. By carrying out the heat treatment of the precursor glass (PG), Er3+ and Cr3+ were selectively partitioned into CaF2 and ZnAl2O4 nanocrystals, respectively. The obtained multi‐phase GC exhibited strong upconversion (UC) fluorescence of Er3+ as well as intense down‐conversion (DC) fluorescence of Cr3+. Under 980 nm excitation, the green UC fluorescence of Er3+ due to 2H11/2,4S3/2 → 4I15/2 transition and the red DC fluorescence lifetime of Cr3+ due to 2E, 4T2 → 4A2 transition were found to be highly dependent on the temperature and makes them possibly suitable for Optical Thermometry. With least‐square fitting methods, the FIR of Er3+ from thermally coupled energy states (2H11/2 and 4S3/2) produced maximum temperature sensing sensitivity values of 0.33% K−1 at 437 K and 0.36% K−1 at 267 K, respectively. Similarly, fluorescence lifetime of Cr3+ attributed to the parity forbidden (2E → 4A2) and spin allowed (4T2 → 4A2) produced the maximum temperature sensor sensitivity value equal to 0.67% K−1 at 535 K.