Ni55Fe19Ga26 ribbons obtained by melt-spinning technique exhibit a martensitic transformation from L2(1) cubic austenite phase to 14 M martensite phase above room temperature. We have taken advantage of the existence of thermal hysteresis of the martensitic phase transition (similar to 11 K) to analyze the effect of isothermal treatments on the reverse martensitic transformation, which has been analyzed by means of interrupted heating using differential scanning calorimetry. The experimental findings clearly indicate a time-depending effect in the martensitic transformation at temperatures between the austenite start and finish temperatures. Moreover, it has been observed that two successive martensitic transformations take place after the isothermal arrest was performed.