The aim of this study was to prepare silver nanoparticles by a green method using the aqueous leaves extract of Lagerstroemia speciosa. The prepared silver nanoparticles were characterized, studied for its photocatalytic and biofilm inhibition studies. The maximum absorbance peak was found at 427 nm and thus confirming the formation of silver nanoparticles. The average size of silver nanoparticles synthesized was found to be 12 nm using XRD and it was spherical in shape. The nanoparticles synthesized was investigated for photocatalytic activity for to two different dye molecules, methyl orange and methylene blue showing 310 and 290 min degradation time respectively. The silver nanoparticles biofilm inhibition assay against clinical strains of Pseudomonas aeruginosa showed lowest accumulation at a lower concentration. The biofilm inhibition was also studied by visual interpretation through Scanning Electron Microscopy states that 50 μg mL− 1 exerts the highest inhibition compared against the control. This evident helps to analysis the silver nanoparticles for various applications in future. © 2017 Elsevier B.V.