The actuation and energy harvesting performance of dielectric elastomers are strongly related to their intrinsic electrical and mechanical properties. For future resilient smart transducers, a fast actuation response, efficient energy harvesting performance and mechanical robustness are key requirements. In this work, we demonstrate that poly (styrene-butadiene-styrene) (SBS) can be converted into a self-healing dielectric elastomer with high permittivity and low dielectric loss which can be deformed to large mechanical strains; these are key requirements for actuation and energy harvesting applications. Using a one-step click reaction at room temperature for 20 mins, methyl-3-mercaptoproionate (M3M) was grafted to SBS and reached 95.2% of grafting ratios. The resultant M3M-SBS can be deformed to a high mechanical strain of 1000%, with a relative permittivity of r = 7.5 and a low tan  = 0.03. When used in a dielectric actuator it can provide 9.2% strain at an electric field of 39.5 MV m-1, and can also generate energy density of 11 mJ g-1 from energy harvesting. After being subjected to mechanical damage, the self-healed elastomer can recover 44% of its breakdown strength during energy harvesting. This work demonstrates a facile route to produce self-healing, high permittivity and low dielectric loss elastomers for both actuation and energy harvesting, which is applicable to a wide range of diene elastomer systems.