Mechanochemically devulcanized ground fluoroelastomer (FKM) was used as a low-cost functional additive for the enhancement of the thermal stability of nitrile–butadiene rubber (NBR) vulcanizates. Without the use of any chemicals, the stress-induced mechanochemical devulcanization of ground FKM was achieved through solid-state mechanochemical milling at ambient temperature. The sol fraction of the ground FKM was increased from its original 1.4 to 19.8% after milling; this confirmed the realization of the mechanochemical devulcanization of FKM. Moreover, the oxygen-containing polar groups on the surface of the mechanochemically milled FKM benefitted its interfacial adhesion with the polar NBR matrix. The curing characteristics and mechanical properties of the devulcanized, FKM-filled NBR vulcanizates were investigated and compared with those of the untreated FKM-filled NBR vulcanizates. The results show that the mechanical properties of the devulcanized FKM-filled NBR vulcanizates were much better than those of the untreated FKM-filled NBR vulcanizates. The presence of the reclaimed FKM significantly increased the onset degradation temperature of the NBR vulcanizates as a result of the improved polymer–filler interaction, uniform dispersion, and high thermal stability of the reclaimed FKM