Abstract: To enhance γ-aminobutyric acid (GABA) content in black soybeans, this study optimized the germination process to significantly increase GABA levels and systematically evaluated the effects of germination on major nutrients, functional components, and antioxidant activities, thereby providing a theoretical basis for developing functional black soybean sprout products. Using black soybeans as the raw material, single-factor experiments investigated the effects of four key factors on GABA enrichment in sprouts and determined the appropriate range for each factor. Subsequently, a Box-Behnken response surface design was employed to optimize these four factors at three levels, establish a mathematical model, analyze factor interactions, predict the optimal process parameter combination, and conduct verification experiments. Additionally, sprouted and unsprouted black soybeans prepared under optimized conditions were analyzed for basic nutrients (protein, fat, total sugar, reducing sugar), functional components (total phenols, total flavonoids), and anti-nutritional factors (phytic acid, sucrose, stachyose, raffinose), and their antioxidant capacities against hydroxyl radicals, DPPH radicals, and ABTS cation free radicals were evaluated. The results indicated that the optimal germination conditions were a soaking temperature of 25 °C, soaking time of 6 h, germination temperature of 24 °C, and germination time of 2 d. Under these conditions, the GABA content in sprouted black soybeans reached 4.14 mg/g, which was 2.23-fold higher than that in unsprouted black soybeans. During germination, protein content initially increased but declined after 3 days. Fat and total sugar contents were significantly reduced by 15.1% and 25.5%, respectively, whereas reducing sugar content increased significantly (P < 0.05). Functional components, including total phenols and flavonoids, increased by 125.1% and 87.0%, respectively. Anti-nutritional factors -phytic acid, sucrose, stachyose, and raffinose -decreased by 54.42%, 82.5%, 92.0%, and 49.23%, respectively. The scavenging capacities against hydroxyl, DPPH, and ABTS radicals were significantly enhanced (P < 0.05). In conclusion, germination significantly increases GABA content, enhances functional properties, and reduces anti-nutritional factors, providing a theoretical foundation and practical support for developing black soybean sprout-based functional foods with improved physiological activity.