Coffee fermentation is a crucial step that significantly influences the final taste and quality of the product. This study investigates the effect of varying wet fermentation durations (0, 12, 24, 36, and 48 hours) on blends of Coffea canephora and Coffea arabica beans. A starter culture of lactic acid bacteria (LAB) was used to enhance fermentation, consisting 2% of Lactiplantibacillus plantarum, Leuconostoc pseudomesenteroides, and Weisella sp., with a consistent Arabica-to-Robusta ratio applied across treatments. Fermentation was carried out at room temperature in a controlled wet environment. After each fermentation period, the beans were dried, roasted, and ground before sensory evaluation. The experiment was conducted in two replicates, and two panelists were involved in the sensory evaluation using the Specialty Coffee Association of America (SCAA) cupping protocol. Panelists assessed aroma, flavor, aftertaste, acidity, body, balance, sweetness, clean cup, overall quality, and final score. Based on the results of the analysis of variance (ANOVA) with a significance value of 0.00, there was a statistically significant effect between treatments (p < 0.05), indicating differences in fermentation and blending times. Fermentation duration had a noticeable impact on sensory attributes. The 48-hour fermentation yielded the highest cupping score, marked by improved acidity, sweetness, and balance, resulting in a cleaner and more complex cup. In contrast, the 12-hour fermentation period showed less flavor development and acidity. In conclusion, controlled wet fermentation with LAB inoculation can enhance the sensory quality of Arabica-Robusta coffee blends. A 48-hour fermentation period was determined to be optimal for producing a balanced, high-quality cup. These findings highlight the potential of microbial starter cultures in improving consistency and flavor development in blended coffee products.