The melt-phase hydrosilylation of terminal double bonds in polypropylene (PP) was investigated. The double bonds were generated by peroxide initiated degradation of PP in an extruder or a batch mixer. For this purpose, an organic peroxide, Lupersol 101, was employed in concentrations of 0.5-5 wt%. A hydride-terminated polydimethylsiloxane was employed as a model substance to investigate the feasibility of hydrosilylating the terminal double bonds of the degraded polypropylene. Reactive processing experiments were carried out in a hot press, a batch mixer, and a single screw extruder. Two different reaction mechanisms were used to initiate the hydrosilylation reaction: a radical chain addition mechanism and a platinum catalyzed mechanism using Karstedt＇s catalyst. For the radical mechanism, it was shown that catalytic amounts of a peroxide could initiate the addition of silanes to the double bonds of the degraded polypropylene. Furthermore, it was found that both reactions, degradation and hydrosilylation, could be performed simultaneously. For the catalytic mechanism, the required stabilization of the platinum colloid formed in this mechanism was accomplished by adding t-butylhydroperoxide as a cocatalyst. This melt-phase hydrosilylation route may be used to produce terminally functionalized polypropylenes, and a case study involving the terminal attachment of a styrene functionality was examined.