This article investigated the synthesis of silver nanoparticles from Ulva lactuca with their antiviral and antioxidant activity. The optimization of nanoparticle synthesis was also regulated. Ulva lactuca was collected in June 2020, prepared, and optimized for silver nanoparticle synthesis. Confirmation of the formation of the silver nanoparticles by Ulva lactuca aqueous extract was determined by UV–VIS spectrophotometer. The nanoparticles were found to be distinct, regular, and primarily spherical, with sizes ranging from 4.08 - 27.57nm, and the average size of particles was found to be 10.29 nm. Silver nanoparticles synthesized from Ulva lactuca showed significant antioxidant activity but less than conventional ascorbic acid. It also showed important cytotoxic activity against the VERO cell line but weak antiviral activity against Adenovirus. The effect of reaction time, AgNO3 Solution to algal extract, precursor concentration, temperature, time, and pH on silver nanoparticle synthesis was evaluated. Characterization of the produced nanoparticles was also performed.