Silver nanoparticles were synthesized from Ehretia laevis Roxb. leaf extract by one-step green synthesis method. The nanoparticles were crystalline in nature, spherical shaped with 25 to 35 nm diameter. The aim of this study was the synthesis and characterization of silver nanoparticles from Ehretia laevis Roxb., and the evaluation of their antimicrobial, anticancer, larvicidal and methylene blue dye degradation efficiency. The nanoparticles showed antimicrobial, larvicidal and cytotoxic activity. At a concentration of 25 µg/mL, it killed 70 ± 10.24% of Culex quinquefasciatus larvae after 72 h treatment. The median lethal concentration of the nanoparticles against HeLa, human cervical cancer cells, and MCF-7 human breast cancer cells, were calculated to 12.7 µg/mL and 14.5 µg/mL, respectively. The synthesized nanoparticles degraded Congo red ~ 85% within 8 h at a concentration of 200 µg/mL. Possible application of the synthesized nanoparticles are water purifying agent in presence of sunlight.