The poly(hedral oligomeric silsesquioxane) (POSS)/silicone rubber (SR) crosslinked rubber composites reinforced were prepared by using laboratory type internal mixer at pre-optimized conditions. The POSs was used to enhance the adhesion properties of SR to reinforcing fibers such as Kevlar and Rayon. Three different POSS types including different functional groups were selected. These functional groups were expected to provide crosslinking with SR and grafting to fiber surfaces. The POSS type and the POSS loading level and reinforcing the fiber type (Kevlar and Rayon) were handled as experimental parameters. The fiber/silicone adhesion was investigated by H-adhesion tests. In addition the thermodynamic work of adhesion (TWA) was determined by using the surface free energy components of the compounds and fibers. The correlation between adhesion strength values and the TWA was investigated to understand the adhesion mechanism. It was found that H- adhesion tests showed an increased adhesion values by the addition of POSS particles. It was seen that there is a linear correlation between H-adhesion values and TWA. Keywords: Silicone Rubber, POSS, Reinforcing Fiber, H-Adhesion, Thermodynamic Work Adhesion Acknowledgement: This study is granted by The Scientific and Technological Research Council of Turkey (TUBITAK) (Project No: 113M258).