The magnetic tape cartridge includes a magnetic tape that is accommodated in the magnetic tape cartridge while being wound around a reel hub. The magnetic tape has a non-magnetic support and a magnetic layer including ferromagnetic powder, and includes one or more components selected from the group consisting of a fatty acid and a fatty acid amide in a portion on the magnetic layer side on the non-magnetic support, and after the magnetic tape cartridge is stored in an environment of an atmosphere temperature of 60° C. and a relative humidity of 80% for 24 hours, a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed at a photoelectron take-off angle of 10 degrees on a surface of the magnetic layer in an inner region during winding of the magnetic tape is 45 at % or more.