Black persimmon, rich in antioxidants and dietary fiber, is gaining popularity due to its potential health benefits. This study investigated the development of black persimmon (Diospyros lotus L.) jam as a functional food, focusing on its nutritional value and potential health benefits. Jam was prepared using a boiling process and then comprehensively evaluated for its nutritional profile (proximate and mineral analyses), phytochemical content, and sensory characteristics (color, aroma, taste, texture, and overall acceptability). The proximate composition of the jam revealed carbohydrates as the most abundant component (73.33%), followed by fiber (11.08%), while the mineral analysis identified the significant presence of potassium (608.66 mg/100 g), alongside other essential minerals like calcium, magnesium, zinc, and iron. In-depth comprehensive in vitro analyses showed that our jam exhibited excellent physicochemical properties, including higher total soluble solids (70°brix), a good titratable acidity (1.09%), an optimal pH (3.33), and a rich phytochemical profile, containing significantly high levels of phenols (8.76 mg/g), flavonoids (1.91 mg/g), tannins (39.01%), TPC (3.72 g GAE/100 g), TFC (0.898 g CE/100 g), and ascorbic acid (112.39 mg/g). Furthermore, our jam also possessed good antioxidant potential, displaying DPPH radical scavenging activity (15.01%) and FRAP (552.04 μmol of Fe2+/g). The sensory assessment revealed that the jam received very high acceptability scores from consumers, particularly for its taste and overall acceptability. In conclusion, this study successfully developed a black persimmon jam enriched with phenols and antioxidants, offering consumers a delicious and potentially functional food option and suggesting its good market potential.