Aim: The study aimed to evaluate the effect of thermal treatment using deep cryogenic treatment and autoclaving on the cyclic fatigue resistance of reciprocating nickel-titanium (NiTi) instruments. Methods: Thirty primary reciprocating (WaveOne Gold, Dentsply India) nickel-titanium instruments, size 25, 0.07 taper, were divided randomly into three groups: cryo-treated NiTi reciprocating files (Group-A), non-treated NiTi reciprocating files (Group-B) and autoclaved NiTi reciprocating files (Group-C). The instruments of groupA were completely immersed in a cryocan containing liquid nitrogen (-196^o C) for 24 h. After 24 h, the instruments were removed from the bath and allowed to gradually return to room temperature. The instruments in group C were autoclaved (121^o C) and allowed to gradually return to room temperature. The files were instrumented (at 350 rpm in 150^o CCW and 30^o CW) in an artificial canal with a curvature of 60^o until fracture. The time offracture was recorded with a stopwatch in seconds and subsequently converted several cycles to fracture (NCF). The results were compared using One-way ANOVA and Tukey’s post-hoc test at a level of statistical significance of 0.05.Results: The mean number of fatigue cycles for the cryo treated group was significantly higher, followed by the non-treated group and the least in the autoclave group. Conclusion: Thermal treatment affected cyclic fatigue resistance. Deep cryo treatment enhanced the cyclic fatigue resistance of reciprocating NiTi files.