Based on a previous model compound study, we investigated the melt reactivity of Si-H and Si-vinyl end-functionalized siloxane oligomers towards polybutylene terephthalate (PBT) in the presence of platinum(0)-catalyst. We clearly observed grafting of the Si-H functional oligomer onto PBT and have also indications for grafting of the Si-vinyl oligomer. The grafting efficiencies and kinetics of both siloxane model compounds are compared and roughly quantified by infrared spectroscopy. This result indicates that the same reactive groups that are used to vulcanize silicone gums at high temperature can also be used to favor compatibility with a polyester matrix, opening perspectives toward polyester-siloxane thermoplastic elastomers.