Sclerotinia disease is one of the most devastating fungal diseases worldwide, as it reduces the yields of many economically important crops. Pathogen-secreted effectors play crucial roles in infection processes. However, key effectors of Ciboria shiraiana, the pathogen primarily responsible for mulberry sclerotinia disease, remain poorly understood. In this study, we identified and functionally characterized the novel effector Cs02526 in C. shiraiana. Cs02526 could induce cell death across various plant species, including mulberry, tobacco, tomato, and strawberry. Moreover, Cs02526-induced cell death was mediated by the leucine-rich repeat receptor-like kinase BAK1, dependent on a 67-amino acid fragment. Notably, Cs02526 homologues were widely distributed in hemibiotrophic and necrotrophic phytopathogenic fungi, but the homologues failed to induce cell death in plants. Pre-treatment of plants with recombinant Cs02526 protein enhanced resistance against both C. shiraiana and Sclerotinia sclerotiorum. Furthermore, the pathogenicity of C. shiraiana was diminished upon spraying plants with synthetic dsRNA-Cs02526. In conclusion, our findings highlight the cell death-inducing effector Cs02526as a potential target for future biological control strategies against plant diseases.