Dielectric elastomers (DEs) are a new type of smart materials showing promising functionalities as energy harvesting materials as well as actuating materials for potential applications such as artificial muscles, implanted medical devices, robotics, and micro-electro-mechanical systems due to their high electromechanical efficiency, stability, lightweight, low cost, and easy processing. Despite the advantages of DEs, a high electric-field is required for the actuation of DEs, which limits the practical applications especially in biomedical fields. We tackle this problem by introducing the multiwalled carbon nanotubes (MWNTs) in DEs to enhance their relative permittivity and to generate their high electromechanical responses with lower applied field level. This work presents the dielectric, mechanical and electromechanical properties of DEs filled with MWNTs. Laser Doppler vibrometer is utilized to directly detect the enhancement of the actuation strains of DE nanocomposites filled with MWNTs. All the results demonstrate the effective improvement in the electromechanical properties of DE nanocomposites filled with MWNTs under the applied electric fields.