Metallic nanoparticles have found various biomedical applications due to their intrinsic physicochemical properties. As the size decreases, the high surface area of particles gives rise to distinctive features, which are entirely different from that of a macro-sized structure. Several methods are involved in synthesizing metallic nanoparticles, and in general, it can be categorized into either bottom-up or top-down approaches. The top-down method consists of cutting down the bulk materials into nano-sized particles through physical, chemical, or mechanical treatments, whereas, in a bottom-up approach, nanoparticles are formed by joining individual atoms or molecules. The top-down approach produces metallic nanoparticles in naked form, which can further agglomerate and hence not suitable for biomedical applications. The bottom-up approach involves solid-state, liquid state, gas phase, biological, microfluidic-technology based, and other methods. Chemical reduction in the bottom-up approach is the most common method of metallic nanoparticle synthesis, which is flexible, simpler, inexpensive, and produces particles in homogenous form. Recently biological method of nanoparticle synthesis has become popular due to its toxic-free nature, inexpensiveness, sustainability, and eco-friendly. In this chapter, we describe the top-down and bottom-up approach and current trends in the synthesis of metallic nanoparticles for biomedical purposes. Further, it explains how the parameters can be tuned to get metallic nanoparticles with the desired shape, size, morphology, composition and crystallinity. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021.