In this review, we describe the contribution of peptides to the biomedical applications of metallic nanoparticles. We also discuss strategies for the preparation of peptide-nanoparticle conjugates and the synthesis of the peptides and metallic nanoparticles. An overview of the techniques used for the characterization of the conjugates is also provided. Mainly for biomedical purposes, metallic nanoparticles conjugated to peptides have been prepared from Au and iron oxide (magnetic nanoparticles). Peptides with the capacity to penetrate the plasma membrane are used to deliver nanoparticles to the cell. In addition, peptides that recognize specific cell receptors are used for targeting nanoparticles. The potential application of peptide-nanoparticle conjugates in cancer and Alzheimer's disease therapy is discussed. Several peptide-nanoparticle conjugates show biocompatibility and present a low degree of cytotoxicity. Furthermore, several peptide-metallic nanoparticle conjugates are used for in vitro diagnosis.