Sewage discharge is considered to be the primary source of viral contamination in aquatic environments. This study was conducted to evaluate the impact of El-Rahawy wastewater on the water quality of the Rosetta branch of the River Nile (Rosetta River Nile) through detection of astrovirus (AstV) and norovirus (NoV) in the water and sediments of both sites. For this purpose, we collected 72 wastewater and 12 sediment samples from El-Rahawy drain, and 12 river water and 12 sediment samples from Rosetta River Nile before and after mixing with El-Rahawy wastewater between April 2017 and March 2018. AstVs and NoVs were identified in wastewater (40.2% versus 25%), El-Rahawy sediment (41.6% versus 20.8%), river water after mixing with wastewater (25% versus 16.6%), river water before mixing with wastewater (8.3% versus 0%), river sediment after mixing with wastewater (16.6% versus 8.3%), and no viruses were found in river sediments before mixing with wastewater. AstV genogroup B and NoV genogroup GI were the most frequently detected genotypes in the analyzed samples, with a peak incidence in the winter months. Increasing detection rates of both viruses in El-Rahawy drain samples and river water taken from the Rosetta branch after receiving El-Rahawy wastewater reflect the impact of this drain on the water quality of this stretch of the River Nile.