Pyrotechnic separation devices have been widely used in various missions of spacecraft in order to separate the structural parts with high reliability. Although they afford advantages of cost-effectiveness and high reliability, pyrotechnic separation devices generate an intensive dynamic response called pyroshock, which can lead to fatal damage to the mounted electronic equipment. Previous studies have attempted to resolve these issues with a shock isolator. However, these studies have limitations such a possible dynamic instability in low frequency and complexity in design. In the present study, a novel design of the sandwich insert is proposed to achieve enhanced shock attenuation without a shock isolator. Static-load tests were conducted to validate the structural performance of the shock-absorbing insert. In order to observe the attenuation performance, shock propagation and response experiments were carried out with consideration that the inserts were utilized to connect parts and to mount devices on the panel. In addition, swept sine vibration tests were carried out to investigate the dynamic response in low frequency. The shock-absorbing insert reduced propagating shock for the joint structure, and the shock response of the mounted equipment was significantly attenuated. The novel shock-absorbing insert saves space and is dynamically stable, and furthermore has the ability to protect the small electronic equipment, which is mounted on the honeycomb sandwich panel, from severe shock. These advantages make it a suitable insert for space structure application for connecting parts or mounting equipment.