<p>A magnetic tape cartridge includes a cartridge casing formed by upper and lower casing halves and a single reel around which a magnetic tape with a leader pin fixed to its leading end is wound and which is contained in the cartridge casing for rotation. A spring member removably holds upper and lower end portions of the leader pin on the cartridge casing. The spring member includes upper and lower holding portions which are respectively brought into abutment against the upper and lower end portions of the leader pin and are connected to each other. <IMAGE> <IMAGE></p>