The present invention provides a recording tape cartridge in which an ability to assemble a security tag into a case is excellent. A recording tape cartridge has: a case that accommodates a reel on which a recording tape is wound; a security tag having a substantially pillar shape, that is provided within the case, and that is adapted to transmit to and receive from an exterior; a holding member that is provided within the case, and that holds the security tag at a first end side of the holding member; and a portion to be fit that is formed within the case, and which is held by being fitted with a second end side of the holding member.