In this study, a dual frequency liquid crystal (DFLC) consisting of low molecular weight liquid crystals (LCs) was newly prepared, and the electrorheological (ER) properties were investigated. The liquid crystalline properties of the mixture were analyzed by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), and the results revealed that the mixture exhibited a smectic A phase. The DFLC mixture showed the ER effects by switching the frequencies, and the change in the viscosity was found to be affected by the given frequencies. Interestingly, the ER effect in the smectic A phase was different from the one observed in the nematic phase.