In the present work, the breakup mechanism of highly viscous epoxy paints discharged from a fan spray nozzle was examined experimentally. The paints tested were non-Newtonian fluids, composed of epoxy resin, solid particles and other additives. The paint spray discharged from the nozzle was visualized and recorded using a digital camera with back illumination. Due to presence of the solid particles, perforation of liquid sheet was observed in most cases, even at low-Reynolds number conditions (Re < 15,000) where the aerodynamic-wave breakup mode is used to be dominant for pure liquids. However, with the increase of the particle concentration, the sheet became longer and the thickness at breakup became thinner to some extent. This is because, with higher concentration of solid particles, the stabilizing effect by the viscosity increase predominates over the destabilizing effect by perforation.