To provide a data recording tape cartridge which prevents deviation in the transverse direction of a tape reel assembly in the locked state.

The tape reel assembly includes a hub, upper and lower flange parts facing each other, brake teeth, and an inside surface. The inside surface demarcates an engagement section of a position separated from the brake teeth. A brake main body includes a stem, a head, a toothed section, and a centering structure. The centering structure is radially extended outward from the head and forms a peripheral edge a radial gap apart from the toothed section. A spring is arranged around a post formed by a cover and deflects the brake main body to the lock state. In the lock state, the toothed section is engaged with the brake teeth to stop rotation of the assembly. Movement in the transverse direction of the assembly is limited by mutual action between the peripheral edge and the engagement section.