In this study, polydopamine (PDA) was used to modify polystyrene/nickel (PS/Ni) metal composite microspheres prepared by chemical plating technology to obtain PDA@PS/Ni microspheres with a size of 2.45 μm. These microspheres were added to a polyurethane pressure-sensitive adhesive (PSA) matrix, and each anisotropic conductive adhesive (PDA@PS/Ni-ACA) was ultimately obtained by rapid UV curing under room temperature conditions. The effects of different loading amounts on the prepared PS/Ni metal composite microspheres were investigated, and the differences in dispersibility, electrical properties, and mechanical properties between PDA@PS/Ni-ACAs and PS/Ni-ACAs were discussed. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), high resistivity measurements, and X-ray photoelectron spectroscopy (XPS) were used to characterize the metal composite microspheres and ACAs. When the PDA@PS/Ni content was 3 wt.%, the resistivity was found to be 1.3 × 10⁻⁴ Ω cm, which is 15 orders of magnitude lower than that of pure PSAs PDA@PS, and the tensile strength was as high as 16.21 MPa. The tensile strength of pure PSA is 18.13 MPa, which is higher than that of heat-cured PSA. In addition, the conductive adhesive maintains its anisotropy when the PDA@PS/Ni content is increased to 30 wt.%. These findings will help to expand the application of ACAs in the electronic packaging industry.