A tape cassette includes a housing. The housing includes a top wall having a top surface and a bottom wall having a bottom surface. The bottom surface has a first surface portion being a flat surface portion and a second surface portion being a flat surface portion. The second surface portion extends generally parallel to the first surface portion and is located between the top surface and the first surface portion in a first direction. The first direction is orthogonal to the top surface or the first surface portion. A first indicator portion is provided on the second surface portion. The first indicator portion has a first protrusion protruding from the second surface portion. The first protrusion has a protruding end being located between the second surface portion and the first surface portion in the first direction.