The effect of a number of thiophosphoryl compounds [viz., bis(isobutyl) thiophosphoryl di-, tri-, and tetrasulfides and bis(dicyclohexyl) thiophopsphoryl di-, tri-, and tetrasulfides] on natural rubber (NR)-carboxylated nitrile rubber (XNBR) blend was studied. All these thiophosphoryl compounds are capable of forming interrubber links leading to covulcanized blends which exhibit a fair degree of synergism with respect to physical properties, the maximum being obtained at the 25% NR and 75% XNBR blend composition. This is an obvious claim that the blend under investigation is technologically compatible, having some degree of interrubber interaction which is enhanced in case of two-stage vulcanization. The existence of interrubber interaction is judged by the swelling experiment. The blend morphology assessed by SEM micrographs corroborates the foregoing observations and accounts for the significant improvement in physical properties of the blend vulcanizates, particularly in two-stage vulcanization.