The benefits of giant electrorheological fluids (GER fluids) have been harnessed to enhance their effect in damping force generation. However, few results have been reported on the issue of taking advantage of a helical duct flow in improving the performance of a GER-based damper in generating and tuning damping effects. In this study, an innovative GER fluid-based damper with helical flow ducts is proposed. The proposed flow mode can achieve a greater pressure gradient during operation, and, thus, improve the damping performance by enlargement of the length of the active region with more compact dimensions. A mathematical model aiming to explain the mechanical properties of the damper is investigated based on the continuity equation and Navier–Stokes equations. Then, simulation studies based on computational fluid dynamics (CFD) solvers are conducted to verify the effectiveness of the mathematical model. Additionally, an experimental prototype of the GER fluid damper is fabricated, and damping force measurements under different excitations are carried out. The experimental results agree well with the results obtained from theoretical analysis and CFD solvers. The regulation coefficient that illustrates the tunable range of the damping force is found to reach a value of 8 times under an electric field ranging from 0 to 1 kV/mm.