This paper studies the rheological properties of shear thickening fluids(STFs) and the performance of a viscous damper filled with an STF by performing a cyclic loading test. A hydraulic steel tube was filled with an STF to develop an innovative passive damper device. A performance test of this device showed that the area and shape of hysteresis loops can vary with different loading conditions. In addition, the hysteresis loops of the developed STF damper under various loading conditions were observed. The experimental results and theoretical study showed that STF-filled dampers are potentially useful in practical engineering applications.