A three-dimensional fluid-structure interaction (FSI) finite element model of a twin gas-chamber hydraulic damper was used to study the high-speed damping characteristics of the damper. The numerical results agreed well with experimental data. The damping characteristics were analyzed for various initial gas chamber volumes and initial pressures with comparisons with a single gas-chamber hydraulic damper. A single pressurized gas sub-chamber in the compression chamber of a monotube hydraulic damper results in more oil cavitation during the compression stroke. The twin gas-chamber hydraulic damper overcomes this problem but still has delayed reverse damping in both the compression and extension strokes. This problem can be reduced by using smaller gas chambers with higher initial gas pressures. The time delay ratio of the damping force reverse increases with increasing piston vibration frequency. The damping force reverse delay ratio in the compression stroke decreases with increasing piston vibration frequency (2.5~15 Hz) for the same vibration displacement, but this ratio in the extension stroke first increases (2.5~10 Hz) and then decreases (10~15 Hz) with increasing frequency. These characteristics are important when designing twin gas-chamber hydraulic dampers.