Abstract: An ink ribbon cassette includes a cassette main body portion rotatably holding a supply core and a take-up core around which the end portions of an ink ribbon are wound and a ribbon guide portion extending to one side from the cassette main body portion and having on one side a ribbon slide contact surface, a ribbon turn-up portion formed at the forward end of the ribbon guide portion being formed by a rotatable roller member, whereby the frictional resistance of the ink ribbon turned up at the ribbon turn-up portion is reduced. Further, the main body portion includes a holder member having the ribbon guide portion and holding the supply core and the take-up core and a case member capable of holding the holder member by holding the supply core and the take-up core in such a way as to cover them from outside, whereby it is possible to provide an ink ribbon cassette which can be easily assembled.