Abstract Background: Due to their wide spectrum of phytochemical components and lack of side effects, the use of plants for the prevention and treatment of cancer has recently attracted increased attention. One among them is Annona muricata, commonly called soursop. According to recent investigations, several types of cancer have been successfully treated using this plant’s extracts. However, studies on oral squamous cell carcinoma (SCC) are very limited. Aim: In the present study, we aimed to investigate the cytotoxic potential of leaf extract of A. muricata (LEAM) against oral tongue SCC-15 cell lines, using in vitro assays. Materials and Methods: 3-(4,5-dimethylthiazol-2-yl)-2,5-dipenyltetrazolium bromide assay was performed to assess cytotoxic activity, and the apoptotic effect was determined using gene expression analyses of Bcl 2-associated X protein (Bax), B-cell C/lymphoma 2 (Bcl-2), and tumor-suppressor phosphoprotein (p53). Results: Significant cytotoxicity (P ≤ 0.05) with a minimum inhibitory concentration value of 40 μg/ml was observed with the LEAM on SCC-15 cell lines. A highly significant decrease was observed in Bcl-2 gene expression (P < 0.05), whereas p53 and BAX genes revealed a highly significant increase (P < 0.05) when SCC-15 cell lines were treated with LEAM in the study group compared to the control. Conclusion: These results show that LEAM has the potential for development as a therapeutic agent for cytotoxicity, particularly on oral SCC cells, following further investigation.