Zucchini (Cucurbita pepo) is a common vegetable crop worldwide. It belongs to Family Cucurbitaceae which is one of the largest plant families and has a high economic impact worldwide. Zucchini can be infected by several plant viral pathogens which cause severe losses in cucurbits production. This study aims to identify certain viruses which infect zucchini in Assiut governorate, Egypt using Reverse Transcription Polymerase Chain Reaction (RT-PCR). The response of four zucchini cultivars (Hytech, Safa, Malat, and 03) to viral infection was evaluated under both greenhouse and field conditions. The assessment was conducted through measuring some parameters including disease severity (D.S), yield, total chlorophyll, and total carbohydrates contents. In general, zucchini cultivars differed significantly in their susceptibility to the infection with Watermelon mosaic virus (WMV) and Papaya ringspot virus (PRSV). Cultivars 03 and Malat were the most tolerant cultivars while Hytech followed by Safa were the most susceptible ones. The obtained data showed that zucchini cultivars differ significantly in their total carbohydrate and chlorophyll contents post the infection with WMV and PRSV. The highest chlorophyll and carbohydrates contents were obtained in 03 and Malat cultivars while the lowest chlorophyll and carbohydrate contents were in case of Hytech followed by Safa under both greenhouse or field conditions. Further studies are required to establish safe and eco-friendly strategies to control these viruses.