Zeolitic imidazole frame work, a special class of porous crystalline material with tunable pore size has emerged as a promising candidate for biomedical applications. The present work enlightens the fabrication of methyl gallate encapsulated ZIF-L (MG@ZIF-L) by utilizing red seaweed Gracilaria debilis and evaluating its anticancer potential against lung cancer cell lines A549. The material structure and physicochemical behaviors were systemically investigated using several spectroscopic techniques. Results showed that MG@ZIF-L possessed high loading efficiency, biocompatibility and fast drug release in tumor microenvironment, revealing that ZIF-L would act as a promising drug delivery system for cancer therapy. In vitro anticancer experiments illustrated that MG@ZIF-L exhibited high cytotoxic effects against A549 cells. Fluorescent microscopic analysis confirmed that MG@ZIF-L enhanced intracellular reactive oxygen species, causing mitochondrial dysfunction, releasing cytochrome C, the key factor for apoptosis. Moreover, in vitro and in vivo toxicity studies using PBMC and zebra fish embryo as model systems confirmed the nontoxic nature of MG@ZIF-L. Overall, the present work highlights the possibility of developing MG@ZIF-L nanocomposite as a suitable candidate for lung cancer therapy.