The synthesis of nanoparticles through environmentally friendly methods is a rapidly growing field within nanotechnology, known for its cost efficiency and high performance. Cymodocea serrulate is a seagrass that belongs to the family Cymodoceaceae commonly used to in traditional medicine to treat skin ailments, wounds and muscle related problems. In this study the hydroalcoholic extract of the seagrass was subjected to GCMS analysis and anticancer effect of silver nanoparticles against MCF-7 followed by in silico molecular docking analysis against Estrogen receptor alpha. The study revealed the observation of twenty bioactive compounds and 14 compounds were found to possess biological activity. The in-silico analysis of these compounds against Estrogen receptor alpha (3ERT) showed highest binding affinity of -5.90 kcal/mol with 9,12- Octadecadienoic acid with compared to the standard doxorubicin with a binding affinity of -7.40 kcal/mol. The cytotoxic effect of the silver nanoparticles was analysed using MTT assay with MCF-7 cell line with an IC50 value of 102.03μg/ml and the results inferred 7.02 % cell death at 12.5 µg/ml and 79.38% cell death at 200 µg/ml while Doxorubicin inferred 87.65% at 5µg/ml. The present study provides a foundation for application of Cymodocea serrulate as an effective anti-cancerous agent with novel bioactive compounds for further commercialization compared to synthetic drugs available in the market for treating breast cancer.