There is provided a MTCMOS flip-flop configured to operate at high speed and to reduce leakage current while realizing a retention function in a sleep mode. The MTCMOS flip-flop may include a signal generator adapted to output an internal clock signal or a sleep mode control signal based on changes in a retention signal and an external clock signal, a master latch adapted to latch an input signal and to output a master latch output signal based on the internal clock signal, and a slave latch connected to an actual ground and adapted to latch the master latch signal, to output a slave latch output signal under control of the internal clock signal, and to maintain the latched signal under control of the sleep mode control signal in the sleep mode.