Phlogacanthus thyrsiformis, a valuable medicinal plant frequently employed by ethnic communities for various health concerns, has shown potential against cancer cell lines in lab tests. However, its effectiveness against Dalton’s Lymphoma (DL) cells remains unknown. In our current study, we aim to investigate the phytochemical constituents, antioxidant properties, and cytotoxic effects of P. thyrsiformis extract against the DL cell line. Additionally, we studied its apoptotic effects through fluorescent staining and Scanning Electron Micrograph (SEM) studies. The plant extract revealed the presence of various important phytochemicals such as carbohydrates, phenols, polyphenols, flavonoids, tannins, terpenoids, triterpenoids, alkaloids, and saponins in various degrees. The analysis revealed that the total phenol content and total flavonoid content were present in substantial quantities, suggesting a strong correlation with its potent antioxidant abilities and also showing close IC50 with the reference, ascorbic acid. Effective growth inhibition of DL cells was observed at different treatment concentrations without affecting normal cells. The occurrence of such cytotoxic effects could be corroborated to its apoptotic-inducing properties. Apoptotic cell death was observed in a dose-dependent manner and further morphological changes were evidenced through SEM studies. Our study thus substantiates that P. thyrsiformis is a potent plant with a reservoir of active phytochemicals and is a natural source of antitumor agents against DL cells.