A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium tT is 3.5 μm≤tT ≤5.6 μm, a dimensional change amount Δw in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw ≤20000 ppm, the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)-(a servo track width on an outer side of winding of the magnetic recording medium) > is satisfied, and a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more.