Composite acrylic pressure-sensitive adhesives (PSAs) were synthesized by emulsion polymerization in the presence of montmorillonite (MMT). An examination with X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that both intercalated and exfoliated structures of MMT coexisted in the composites. It was demonstrated by X-ray photoelectron spectroscopy (XPS) that enrichment of the surface by the surfactant during drying of emulsion PSAs was depressed by the layered silicate. Significant improvements in storage modulus and cohesive strength were achieved by incorporation of MMT. The addition of only a small amount of MMT was enough to improve the adhesion properties of acrylic emulsion PSAs.