Lagerstroemia speciosais commonly known as Banaba or Jarul which is used to get rid of various ailments such as fever, urinary infection, decongestion, diarrhoea, mouth ulcers, astringent, diabetes mellitus, kidney diseases, abdominal pains etc. The present work, describes the green synthesis of silver nanoparticles from ethanolic extract of fruits of L.speciosa (Ls-Ag NPs) and their analysis for antimicrobial activities. The characterisation of so obtained nanoparticles have been carried out with help of Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM). Further, antimicrobial activities of ethanolic extract of fruits of L.speciosa(Ee-Ls), silver oxide (Ag2O), and Ls-Ag NPs have been examined by using well-diffusion method against two bacterial strains: Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) and one fungal strain: Aspergillus niger.It has been observed that the biosynthesized Ls-Ag NPs possess much effective antimicrobial activity against selected strains as compared to Ee-Ls and Ag2O.