The present study an effort has been made to developed nanoparticles used to biological and industrial application. The green synthesis of selenium nanoparticles using aqueous extract of Leucas lavandulifolia leaf has been demonstrated. The high biological activity of selenium and its nanoparticles have an extensive range of applications. The healthy Leucas lavandulifolia leaf was collected from Nallampalli, in Dharmapuri district of Tamil Nadu in India. The phytochemically isolated components and the water soluble heterocyclic components such as alkaloid and flavones were principally responsible for the reduction of selenium ions and the stabilization of the nanoparticles. The synthesized selenium nanoparticles are characterized by UV-Visible spectroscopy, FT-IR, SEM, EDX and antibacterial activity. The phytochemical screening test displayed the presence of dynamic phytoconstituent of Leucas lavandulifolia leaf and stem aqueous extracts. The synthesized selenium nanoparticles exhibits spherical shape with average diameter range is 56 nm - 75 nm. Green synthesized selenium nanoparticles could be a potential antibacterial agent.