A procedure to calibrate the temperature measurements in the transient regime of internal IR-laser deflection (IIR-LD) apparatus is presented. For this purpose, a thermal test chip (TTC), whose behavior is analytically well described by a simple model, is used. During the calibration process, the TTC is thermally excited during short heating times (up to 250μs), estimating its internal temperature profile by IIR-LD measurements. Afterwards, experimental results and model predictions are compared. Good agreement between theory and experiment is found when a temperature rise ranging from 0to1.4K is measured. The presented procedure can be also used to thermally calibrate optical probing apparatus for measuring the thermal behavior of power devices, as well as to determine thermal parameters of other materials, such as SiC and GaN. In particular, it should be very useful for the determination of the thermo-optical coefficient (∂n∕∂T)C of such materials. In the present work, a value for (∂n∕∂T)C of 2.0×10−4K−1 is found in silicon, which agrees with literature reported values. The benefits of this method are its simplicity, accuracy, and low time consumption.