Abstract The size- and shape-dependent properties of nanomaterials are one of the highly active areas of research in modern medical sciences applications, especially for antimicrobial effects. The antimicrobial studies of nanomaterials have shown the size-, morphology-, and composition-dependent properties. Furthermore, the fabrication and surface functionality have also played important roles. Silver (Ag) is one of the most studied nanomaterials for various applications, from materials science to biomedical field. Nearly 24% of nanomaterial-based consumer products have engineered nanosized Ag materials. This chapter aims to bring together studies of the substantial antimicrobial effects of nanomaterials and their size- and morphology-dependence. in particular, the chapter focuses on silver (Ag)-, copper (Cu)-, gold (Au)-, and zinc (Zn)-based nanomaterials.