In this paper we discuss the use of photothermal techniques to study first-order phase transitions. The NiTi alloy was used as a probe since it is a well-known material. The phase transition temperatures were determined by differential scanning calorimetry, dilatometry and x-ray diffraction experiments. The results obtained by thermal mirror and photothermal deflection techniques were compared to conventional ones showing good agreement. As far as we know, this is the first time that the thermal mirror has been used to detect and characterize a phase transition in a metal sample.