Abstract: A new kind of low loss ZrTi₂O₆ filled polytetrafluoroethylene (PTFE) microwave composite substrates were fabricated through the hot-pressing process. The microwave dielectric properties of the composites were measured using dielectric resonator method (18-12 GHz). The relative permittivity (ε_r) and loss tangent (tanδ) of the composites increase with an increase of the volume fraction of ZrTi₂O₆ ceramic (0-46%). The experimental dielectric constants of the composites match well with the theoretically predicted values using Lichtenecker model. As the volume fraction of ZrTi₂O₆ ceramic increases, the thermal expansion coefficient and the temperature coefficient of dielectric constant decrease. The ZrTi₂O₆/PTFE composites exhibit a dielectric constant of 7.42 with a loss tangent of 0.0022 (10 GHz) at an optimum filler volume fraction of 46% ZrTi₂O₆.