The addition of colloidal shear thickening fluids (STFs) to Kevlar fabrics has been shown to enhance the ballistic penetration resistance of the fabric, under conditions of low velocities and small target sizes. It is believed that this improvement in ballistic properties is related to the resistance of the STF to deformation at high strain rates, since the addition of Newtonian fluids to Kevlar fabric does not improve ballistic performance. However, the precise role of the STF, and its rheological properties, in the ballistic defeat process are not known. In this study, ballistic and rheological experiments are performed to determine the effect of fluid viscosity, particle loadings, and particle size and shape on the behavior of STF‐Kevlar composites. These results will be help to determine which rheological parameters are most critical to achieving enhanced composite properties.