A nanocrystalline KNbO3 particle/polymer hybrid was synthesized through controlled hydrolysis and polymerization of metalorganics below 100 °C. A KNbO3 precursor was synthesized from potassium ethoxide, niobium ethoxide, and acetoacetoxyethyl methacrylate. The K–Nb alkoxide precursor was hydrolyzed and polymerized yielding KNbO3 particle/polymer hybrid. The organic matrix included nanometer-sized crystalline particles depending upon the hydrolysis conditions. The nanocrystalline particles were identified to be potassium niobate by electron diffraction and energy dispersive x-ray analysis. The suspension of the hybrid in silicone oil revealed a yield stress dependent upon various conditions, such as concentration and applied field. The hybridization was found to have a pronounced effect on the electrorheological properties of the fluid, including the KNbO3 particle/polymer hybrid.