This paper presents a study on the development of a side buffer to absorb the impact energy of colliding railcars. Buffers are essential elements for improving the traveling comfort of passengers and extending the service life of a wagon chassis. In designing the buffer's energy absorption characteristics, a combination of a hydraulic damper and a stack of disc springs (Belleville springs) were utilized. Disc springs have nonlinear load-deflection characteristics; by stacking them in series and parallel arrangements, the desired load-deflection characteristics can be achieved. The finite element method was employed to evaluate the performance of the designed buffer in terms of force-stroke and kinetic, strain, and viscous energies for 5, 7, and 9 km/h impact velocities. Simulation results proved that the designed buffer ensures the requirements of EN 15551 easily for various collision speeds. Low level of acceleration values and small peak collision forces proved that the proposed buffer has superior performance in comparison with the existing buffers in service by improving the shock absorption and crashworthiness features of railcars.