A tire is a composite material reinforced with fabric cords. Natural rubber (NR) is often used as a matrix in tire manufacturing. Natural rubber has many outstanding properties such as high strength, excellent adhesion to brass-plated steel cord, low hysteresis, low rolling resistance etc. Steel cords, steel cables and textile cords such as poly(ethylene terephthalate) (PET), Nylon6.6, Aramid, and Rayon are the reinforcing materials that are widely used in tire production. Polymeric textile cords are commonly treated with resorcinol formaldehyde latex (RFL) solution in order to obtain the desired adhesion between rubber matrix and textile cords. The aim of this study is to eliminate the negative environmental effects of resorcinol formaldehyde latex having some disadvantages such as high cost, toxicity and multistep time-consuming dipping process. For this purpose, poly(hedral oligomeric silsesquioxane) (POSS) a new generation of organic/inorganic hybrid nanofiller having the possibility of increment the adhesion between textile cords and rubbers was used in this study. Methacryl POSS (M-POSS) with reactive functional groups were used as both crosslinking agent and adhesion promoter for NR based rubber compounds. The adhesion between rubber compound and Aramid fiber was investigated by H-adhesion tests. In addition, the thermodynamic work of adhesion (TWA) was calculated by using the surface free energy components of the compounds and the Aramid fiber. The correlations between H-adhesion strength values and the TWA were studied to understand the adhesion mechanism. It was obtained that the directly incorporation of M-POSS to the NR compounds significantly improved the adhesion between Aramid fiber and NR compounds.