Drug repurposing has been an emerging therapeutic strategy, which involves exploration of a new therapeutic approach for the use of an existing drug. Glibenclamide (Gli) is an anti-diabetic sulfonylurea drug extensively used for the treatment of type-2 diabetes, it has also been shown to possess anti-proliferative effect against several types of tumors. The present study was executed to understand the mechanisms underlying the interaction of Gli with DNA under physiological conditions. The binding mechanism of Gli with DNA was scrutinized by UV–vis absorption spectroscopy and fluorescence emission spectroscopy. The conformational changes and electrochemical properties were analyzed by circular dichroism spectroscopy and cyclic voltammetry. Isothermal titration calorimetry was employed to examine the thermodynamic changes and molecular docking technique used to analyze the interaction mode of Gli with DNA. The spectroscopic studies revealed that Gli interacts with DNA through groove binding mode. Further, isothermal titration calorimetry depicted a stronger mode of interaction favorably groove-binding. Recently, systemic combination therapy has shown significant promise in inhibiting multiple targets simultaneously yielding high therapeutic competence with lesser side effects. With this concern, we intended to study the combined cytotoxicity of Gli with doxorubicin (Dox). The results of MTT assay and acridine orange (AO)/ethidium bromide (EtBr) staining showed synergistic cytotoxicity of Gli + Dox combination on HepG2 & A549 cells. The present study documents the intricate mechanism of Gli–DNA interaction and delivers a multifaceted access for chemotherapy by Gli + Dox combination.