AbstractPoly(urea‐formaldehyde) microcapsules filled with epoxy resins(MCEs) were applied to bisphenol A dicyanate ester (BADCy) resin to develop a novel BADCy/MCEs system. The effects of MCEs on the viscosity and the reactivity of BADCy were investigated. The mechanical properties and the hot water resistance of cured BADCy/MCEs systems were evaluated. The morphologies of the cured systems were characterized using a scanning electron microscope. The thermal property of cured systems was investigated using thermogravimetric analysis. The results indicate that MCEs may influence the reaction of BDACy. The proper addition of MCEs can significantly improve the mechanical property and the hot water resistance of cured BADCy resin. MCEs have a negative influence on the initial thermal decomposition temperature (Td) of cured BADCy resin. POLYM. COMPOS., 2010. © 2008 Society of Plastics Engineers.