The morphology and physical properties of dicyandiamide (DICY)-cured epoxy resin modified with acrylic particles were studied. We used one homopolymer of methyl methacrylate (MMA) and three copolymers of MMA and glycidyl methacrylate (GMA) [P(MMA-GMA)] containing different amounts of GMA as the acrylic particles. When a mixture of the acrylic particles and the epoxy resin was heated, the particles were swollen with the epoxy resin and thus a soft gel with no fluidity was formed. Further heating to the reaction temperature of the DICY cured the soft gel. The structure of the acrylic particles strongly affected the physical properties of the soft gel and the cured epoxy resin. The cured system containing 5 mol% of GMA showed the best physical properties (impact strength and adhesive property), but there was a tendency for the physical properties to decline with a higher GMA content. We have determined that the GMA content of the acrylic particles affects the concentration of network chains in the system.