Fine particles of condensation polymers, including engineering plastics, are in high demand for a wide range of applications since their chemical and/or physical properties have been improved compared to traditional radical polymers. However, the production of condensation polymer fine particles must be creative because oil-in-water (O/W) emulsion polymerizations are not applicable and O/W emulsion castings are also limited to those polymers that are soluble in typical less-polar solvents that are immiscible with aqueous media. Herein, we demonstrate that oil-in-oil emulsions can be formed by a ternary system composed of two different polymers and one solvent, which offers spherical templates for the casting of condensation polymers. The ternary system has enabled the production of fine particles of various engineering plastics with narrow size distributions.