Styrene/butyl acrylate (SBt) was prepared using in-situ seed emulsion polymerization and precipitated in an excess of methanol. The prepared (SBt) was utilized as modifier additive for acrylonitrile–butadiene rubber (NBR) in different dosage i.e. 5 phr, 10 phr, 15 phr and 20 phr. The rheometric and the physicomechanical characteristics of the vulcanizates include tensile strength, elongation at break, and swelling in toluene and motor oil were studied at room temperature before and after aging at 90 oC for up to 7 days. Moreover, morphology and dielectric properties of the modified (NBR) vulcanizates were investigated as well. It was discovered that 20 phr of the Styrene/butyl acrylate (SBt) that incorporated with (NBR) has the highest physicomechanical characteristics as well as dielectric parameters.