Cucumis sativus L., commonly known as cucumber, is a member of the Cucurbitaceae family and is commonly consumed in its ripened stage for its high moisture content, low caloric content, and refreshing texture. The present study focuses on the Malini variety of cucumber, which is often discarded at the overripened stage due to undesirable changes in appearance and palatability, resulting in considerable post-harvest waste. This research evaluates the nutritional, phytochemical, and proximate profiles of Malini cucumbers at both ripened and overripened stages to investigate their potential for sustainable food product development. Their proximate composition, including moisture, ash, protein, and fiber content, was determined using AOAC methods. Mineral content was assessed via ICP-OES, and vitamin levels were measured using spectrophotometric techniques. Phytochemical screening was conducted to identify the presence of bioactive compounds such as flavonoids, alkaloids, tannins, saponins, and cucurbitacins using HPLC and GCMS. Proximate analysis revealed that ripened cucumbers contained higher moisture content (97.6%) and amounts of vitamin K (9.6–24 mg per 100 g), while overripened samples exhibited elevated levels of dietary fiber (0.52–0.56%) and phenolic compounds. Cucumber has a modest amount of mineral content, mainly Ca, Cu, Mg, Fe, Na, and Al in the ripened stage, but P and Zn are higher at the overripened stage, and Se and Mo are lowest in both stages. All these compounds are linked to health benefits, including antioxidant, anti-inflammatory, anti-diabetic, anti-carcinogenic, and cardioprotective effects. Despite the rich phytochemical composition of overripened cucumbers, their application in functional foods remains underexplored. This work aims to utilize the nutritional potential of overripe Malini cucumbers to formulate value-added products such as fiber-enriched snacks, fermented beverages, and nutraceutical ingredients. The findings support a sustainable approach to food innovation by converting agricultural surplus into functional food resources, thereby reducing food loss and promoting health through bioactive-rich diets.