Synthesis of nickel nanoparticles using bioreduction (lactobacillus assisted) method, an eco-friendly nano-biotechnological approach is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ni nanoparticles. Individual nanoparticles as well as a number of aggregates having the size of 30-50 nm are found. Possible involved mechanism of biosynthesis has also been discussed.