Gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals which can induce chain scission or crosslinking in the polymer backbone. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of ⁶⁰Co. After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane, and thermal properties were evaluated before Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Finally, the shape memory properties were evaluated both qualitatively and quantitatively, the last one by Thermo-Mechanical Analysis (TMA).