A ribbon cassette capable of maintaining ribbon position includes a shell, two spools, and two guides. The two spools are each rotatably disposed above the shell for transporting the ribbon. The two guides are each disposed at one side of one of the two spools for maintaining the position of the ribbon. The ribbon cassette of the present invention is capable of avoiding shift of the ribbon on the spools in a transportation process of the thermal transfer printer or the ribbon cassette itself. Hence the problem of wrinkles due to such shift is reduced.