Background: Alkaloid- and polyphenol-rich white mulberry leaf and apple peel extracts have been shown to have potential glucose-lowering effects, benefitting the control of postprandial blood glucose levels. This study aimed to determine the effect of the combination of Malus domestica peel and Morus alba leaf extracts (GLUBLOC^TM) on postprandial blood glucose and insulin-lowering effects in healthy adults after a carbohydrate-rich meal or sucrose drink intake. Methods: This study was designed as a randomized, crossover, single-blinded clinical trial. Out of 116 healthy participants, 85 subjects (aged 18–60 years) completed the day 1 and 5 crossover study. On day 1, subjects were supplemented with a placebo or GLUBLOC^TM tablet 10 min before the carbohydrate-rich meal (300 g of tomato rice) or sucrose drink intake (75 g of sucrose dissolved in 300 mL water). On day 5, the treatments were crossed over, and the same diet was followed. Postprandial blood glucose and insulin levels were measured on days 1 and 5 (baseline 0, post-meal 30, 60, 90, and 120 min). Differences in iAUC, Cmax, and Tmax were determined between the placebo and GLUBLOC^TM-treated cohorts. Results: Significant changes in total iAUC (0–120 min), Cmax, and Tmax of postprandial blood glucose and insulin levels were noticed upon GLUBLOC^TM supplementation. The percentage reduction in the iAUC of blood glucose levels was 49.78% (iAUC_0–60min) and 43.36% (iAUC_0–120min), respectively, compared with the placebo in the sucrose drink intake study. Similarly, there was a 41.13% (iAUC_0–60min) and 20.26% (iAUC_0–120min) glucose-lowering effect compared with the placebo in the carbohydrate-rich meal intake study. Conclusions: Premeal supplementation with GLUBLOC^TM significantly reduced the postprandial surge in blood glucose and insulin levels after a carbohydrate-rich meal or sucrose drink intake over 120 min in healthy individuals. This study proves that GLUBLOC^TM can manage steady postprandial blood glucose levels.