Aim: In this study we aim to formulate nanoparticles by green synthesis using miswak, and evaluate the formed particles using UV spectroscopy. The formed silver nanoparticles are then incorporated into a mouthwash. To evaluate the cytotoxic evaluation of the mouthwash on embryonic development of zebra fish. Materials and methods: Miswak mediated silver nanoparticles were synthesised and incorporated along with sodium lauryl sulphate, sodium benzoate, xylitol and peppermint oil along with water to formulate a mouthwash. The nanoparticle formulated was evaluated using UV-vis spectroscopy. For toxicology evaluation silver nanoparticle, the oral rinse was added in various concentration to medium containing developing embryonic zebrafish egg. Results and Discussion: The broad peak recorded in the UV vis spectrophotometer of 350-400nm indicated that the silver nanoparticles were synthesised. The hatching rate of the zebrafish was only affected only in high concentrations and the viability of the zebrafish embryos was above 50 % in all concentrations. The embryo development that when visualised under microscope revealed that the mouthwash containing media didn’t cause any structural and developing abnormality during its development. Conclusions: The results of our study reveal that the silver nanoparticle-based mouth rinse is not toxic to the developing zebrafish in lower concentrations. From the results of our study, we can reveal that smaller green synthesised nanoparticles at the right concentration is not toxic and could be used for purpose of oral hygiene products such as mouthwash