Watermelon mosaic virus (WMV) poses a significant threat to cucurbit crops. Leaves of squash plants showing viral like symptoms similar to the typical symptoms of WMV were collected from Assiut governorate, Egypt and mechanically inoculated into healthy squash plants. Total RNA was extracted from symptomatic infected squash leaves and reverse-transcription polymerase chain reaction (RT-PCR) was conducted using specific primers to amplify Coat Protein (CP) of WMV. The results of RT-PCR confirmed the identification of WMV. To assess the impact of application of six fungal isolates to control WMV, two experiments were conducted in two different seasons, employing three distinct application methods, namely seed coating, soil drenching, and foliar spray. The results indicated a noteworthy reduction in disease severity of WMV based on symptom development, with an average reduction of 52.0% compared to the infected control group. Different fungi varied in their ability to reduce the disease severity. The efficacy of fungal bioagents in controlling WMV was also influenced by the application method. On average, Seed coating with fungal bioagents exhibited the highest reduction in disease severity (54.2%), followed by foliar spray (51.5%) and soil drenching (50.0%). In addition, these treatments had an impact on the chlorophyll content, where a significant increase in chlorophyll content was observed in the treated plants compared to the infected control group, with an averaged increase of 62.7%. These results suggested that using fungal bioagents could be useful to reduce the disease severity of WMV in squash plants.