Thermoplastic vulcanizates (TPVs) are multifunctional materials consisting of two or more phases with solid elastomeric properties at room temperatures and fluid-like properties when heated. They are produced via dynamic vulcanization process. They exhibit both the high elasticity of the conventional rubbers and good processability with recyclability of thermoplastics. The most widely produced TPV type is PP/EPDM, which is the focus in this study. The peroxides are mostly selected to be used in crosslinking of TPV, since peroxides gives crosslinking through both saturated and unsaturated bonds and they yield low permanent set and high temperature resistance. However, they still have some disadvantages such as the side reactions resulting the beta chain scission of PP phase and undesired disproportionation reactions. In order to eliminate these disadvantages, coagents are used. Coagents make crosslink bridges between elastomer chains and increase the crosslinking efficiency of peroxide by decreasing the side reactions. In this study, for the first time in the literature the potential use of polyhedral oligomeric silsesquioxane (POSS) moieties having unsaturated bonds will be investigated as a coagent in PP/EPDM based TPV production via dynamic vulcanization. The POSSs are Si-O nanocages having different varieties of chemical functionalities. In this study, peroxide crosslinked PP/EPDM/POSS system was dynamically vulcanized in a lab-scale microcompounder (Xplore Instruments, The Netherlands). Octavinyl-POSS (OV-POSS) was used as the POSS type. Rheological and thermal properties of the TPVs having OV-POSS was compared with the TPVs produced using a conventional coagent.