This review article focuses on recent advancements in enhancing the mechanical, thermal, electrical, and corrosion-resistant properties of epoxy resin through the incorporation of surface-modified zinc oxide nanoparticles. The main objective of this review is to highlight the role of nanoparticle surface modification and weight fraction on the performance of epoxy nanocomposites and to provide a comprehensive overview of the findings reported in previous studies. In this review, scientific articles and experimental studies on epoxy nanocomposites containing zinc oxide nanoparticles were systematically analyzed. Selected studies were evaluated based on criteria such as the type of nanoparticle surface modification, dispersion and mixing methods, nanoparticle weight fraction, and the effects of these parameters on the mechanical and thermal properties of the epoxy matrix. Additionally, the findings related to hybrid nanocomposite structures and their synergistic effects were summarized. The review indicates that uniform dispersion of nanoparticles in the epoxy matrix improves interfacial adhesion, prevents stress concentration and crack propagation, and consequently enhances the overall strength and durability of the material. Most studies suggest that low nanoparticle loadings (0.25–1 wt.%) promote better dispersion and improved mechanical properties, whereas higher loadings may cause particle agglomeration and reduced performance. Surface modification of nanoparticles with silane or amine groups enhances compatibility with the polymer matrix, improves stress transfer, and increases thermal stability. Furthermore, recent studies show that hybrid nanocomposite structures create synergistic effects, simultaneously enhancing multiple performance characteristics. Overall, the incorporation of surface-modified nanoparticles into epoxy resin demonstrates significant potential for developing advanced materials in electronics, photonics, marine, medical, and aerospace applications.