A tape cartridge is detachably installed on a cartridge installation portion of a tape printing apparatus having the cartridge installation portion and a press switch. The cartridge installation portion has an installation base portion and an installation peripheral wall portion surrounding the installation base portion and allows the tape cartridge to be installed on the cartridge installation portion. The press switch has a stem projecting in a direction crossing an installation direction of the tape cartridge and provided on the installation peripheral wall portion. The tape cartridge includes a detected portion that is provided on an outer peripheral surface of the tape cartridge and corresponds to the stem when the tape cartridge is installed on the cartridge installation portion. The detected portion has an installation guide slant surface that presses the stem when the tape cartridge is installed on the cartridge installation portion.