Buckwheat is important not only as a crop that improves soil quality and reduces erosion, but its excellent nutritional profile for usage in functional foods. This study aimed to investigate how long-term storage (3, 6, and 9 months) affects Novosadska variety buckwheat's chemical, nutritional, and antioxidative properties, phenolic acids and bioflavonoids profiles. Standard traditional methods were used for quality determinations, and instrumental (spectrophotometry, reverse-phase high performance liquid chromatography) for antioxidant activity and bioactive compounds determination. One-way ANOVA, and Tukey’s HSD post-hoc were performed for statistical data processing. Throughout the storage period, proximate composition and starch content significantly decreased (p<0.05), while total carbohydrates, β-glucan, and energy value significantly increased (p<0.05). Significant decrease in pH and alcoholic acidity of 0.55 pH units, and 0.33% DM, were observed. Total phenol content and antioxidant activity decrease to 5.57 mg GAE/g DM TPC, 22.20 μmol Fe2+/g DM FRAP and 8.12 μmol TE/g DM DPPH, during the storage (p<0.05). Of fifteen phytochemical compounds, gallic, p-coumaric, trans-cinnamic acids, and epicatechin were in high abundance, with a notable decrease in epicatechin (38%). To the authors' knowledge, dihydrocaffeic and phloretic acids, daidzein, naringin, and naringenin were quantified in buckwheat flour for the first time. Easy adaptability to the environment, ability to attract various insects, speedy short-season growing plant for food, many nutritional and health benefits, gives buckwheat potential to be sustainable and biodiversity-friendly crops.