The role of phenolic resin tackifier on autohesive tack of brominated isobutylene-co-p-methylstyrene (BIMS) rubber was studied by a 180 peel test with particular reference to aging. Phenolic resin showed very little effect on the unaged tack of BIMS rubber. The tack strength of the rubber/resin mixture marginally increased at 1phr resin concentration, beyond which it decreased. Based on the data on the compression creep, maximum tensile stress, and viscoelastic properties of the rubber/resin mixtures, phenolic resin did not enhance the interfacial viscous flow behavior of the rubber/resin mixtures. The results from dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) confirmed the existence of a phase-separated morphology in the rubber/resin blends even at low resin concentration. Upon aging at 100C for 36h, the rubber/resin blend containing 1phr of phenolic resin showed further increase in tack strength which was attributed to migration of the tackifier to the rubber surface and the changes in the compression creep, viscoelastic behavior, and maximum tensile stress of the rubber/resin mixtures. This is also a function of aging time. Surface energy analysis by contact angle measurement, Fourier Transform Infrared Spectroscopy (FT-IR/ATR) studies, and surface roughness measurement by atomic force microscopy (AFM) elucidate the enrichment of the phenolic resin on the rubber surface upon aging and the mechanism of enhanced tack strength.