A tape cassette includes a cassette case, a tape roll, a tape feed roller, and a head insertion portion. The cassette case has a top face, a bottom face, a front face, a rear face, a pair of side faces and a connecting face. The pair of side faces includes a left side face and a right side face that are opposed to each other. The tape feed roller is provided on a right side of the left side face and is provided in a front left corner portion. The head insertion portion is configured such that a head of a printer is inserted thereinto. The head insertion portion is an opening that is formed on a right side of the tape feed roller and extends from the bottom face toward the top face. At least one third line passes through the head insertion portion.