We report on electrical insulating materials that not only have sufficient mechanical toughness to survive use conditions but also possess the ability to undergo thermally induced self-repair when damaged. By controlling the cross-link density, a modified ethylene-octene copolymer (EOC) is able to retain its self-healing abilities while also being used at temperatures greater than the original, unmodified polymer. Specifically, an EOC cross-linked with 0.25 wt % dicumyl peroxide affords a material ability to recover 61% of its critical fracture energy-a value similar to thermoplastic EOC. Furthermore, as shown by dielectric spectroscopy, the cross-linked EOC retains good electrically insulating properties.