A magnetic recording cartridge includes a magnetic recording medium of which an average thickness tT is tT≤5.6 μm, a dimensional change amount Δw in a width direction with respect to a tension change in a longitudinal direction is 660 ppm/N≤Δw, and a squareness ratio in a vertical direction is 65% or more, in which the magnetic recording medium is accommodated in a state of being wound around a reel 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)>0 is satisfied.