A tape cassette configured to accommodate a tape has a cassette case having first-sixth outer walls, a substrate having first and second surfaces. A storage is provided to the second surface. The third wall is formed with a first recess having a bottom wall, which is formed with a second recess or a hole. The substrate is arranged in the first recess with an adhesive layer being sandwiched between the bottom wall and the second surface. The storage or a molded part protecting the storage is arranged in the second recess or the hole. The first recess is formed with an opening part, at least a part of the adhesive layer being accessible through the opening part, and the cassette case is provided with a blocking member overlapping the one of the storage and the molded part in a first direction at the particular position.