Breadfruit leaves (Artocarpus altilis (Parkinson ex F.A. Zorn) Fosberg) belonging to the Moraceae family are one of the plants that can be used as traditional medicine that is found near all regions in Indonesia. Breadfruit leaves (Artocarpus altilis (Parkinson's ex F.A. Zorn) Fosberg) have a high antioxidant activity that can be used as an alternative therapy in the treatment of cancer. The purpose of this study was to determine the cytotoxic activity of ethyl acetate extract of breadfruit leaves (Artocarpus altilis (Parkinson's ex F.A. Zorn) Fosberg). Observation of cytotoxic activity using the Brine Shrimp Lethality Test method with various test concentrations of 1000 μg / ml, 100 μg / ml, 10 μg / ml. The results of the study found that the percentage of death from each test concentration was different, namely 100%, 83.33% and 56.66%. Ethyl acetate extract from breadfruit leaves (Artocarpus altilis (Parkinson's ex F.A.Zorn) Fosberg) has cytotoxic activity with a value of ,LC-50. 11,180 μg/ml belongs to the category of highly toxic. Research can be concluded that breadfruit leaves (Artocarpus altilis (Parkinson's ex F.A. Zorn) Fosberg) have the potential to have cytotoxic activity.