Because of rapid industrialization, contaminants such as heavy metals, different types of dyes, pharmaceutical waste, and chlorinated compounds are constantly dumped in nature in recent years. The elimination of these pollutants from the atmosphere is a big challenge in the world. If they are not treated may cause an adverse effect on the ecosystem and human health. In recent years, remediation by nanotechnology has received much attention due to the unique physical and chemical properties of nanoparticles. A combination of bioremediation and nanotechnology known as nanobiotechnology could overcome the limitations of traditional methods as nanobioremediation is eco-friendly and reduces the cost for removal of contaminants. Among microorganisms, bacteria are preferred for nanoparticle synthesis as of their high growth rate and more biomass protection ability. Several metals are used for the synthesis of bacteria nanoparticles including silver, platinum, gold, palladium, titanium, etc. The bacteria have the ability to produce nanoparticles with diverse size, shape, and composition with diverse physical and chemical properties and have more efficacy than bulk materials due to large surface-to-volume ratio, easy handling, economic viability, and high reactivity. This section focuses on the outline of synthesis of bacterial reduced nanoparticles, their mechanisms, factors affecting the nanoparticle synthesis, and their application in bioremediation.