Presented in this paper is an approach to the optimal design of a buffer for a buffered impact damper. The buffer of a buffered impact damper is modelled as a spring-damper pair. For a buffered impact damper to achieve effective vibration control and at the same time eliminate the inherent disadvantage of the conventional impact damper (i.e. high contact force resulting from impact and high acceleration and noise resulting from high contact force), the design of the buffer is formulated so as to maximize the impulse of impact, thus maximizing the momentum exchange between the damper mass and the primary structure to be controlled, subject to a limit on the maximum impact force. This problem is solved via the production of a design chart. Experiments and numerical simulations demonstrate that the impact damper with the buffer produced from this design approach can not only significantly reduce the contact force and peak value of the acceleration generated by collisions, but also enhance the vibration control effect, which makes it ideal and applicable for general engineering applications. Copyright © 2009 John Wiley & Sons, Ltd.