Recent advancement in the synthesis of inorganic nanoparticles provides scientists a wide range of nanomaterials for their research. Biomedical applications of inorganic nanoparticles have received much attention because of their potential to carry out specific tasks inside our body. To make these small particles compatible and functional inside a human body, designed organic groups are usually attached onto the surface of these particles. In this chapter, we focus on three most commonly used functional inorganic nanoparticles (gold, iron oxides, and quantum dots) for biomedical applications. Gold nanoparticles can be used as a contrast agent for CT scans. Iron oxides nanoparticles have already been used in clinical trials as a contrast agent for MRI scans. Quantum dots can provide strong luminescence for labeling cells and other biological species. Synthesis, functionalization and applications of these inorganic nanoparticles will be discussed.