Soy sauce is a traditional brown liquid condiment widely used in Asian cuisine to enhance taste and flavor. In Cambodia, the quality of local soy sauce products remains limited. Koji mold is the key microorganism used to improve the quality of soy sauce. This study aimed to improve the quality of soy sauce by using different koji molds including Aspergillus oryzae and Aspergillus sojae. The physicochemical characteristics of koji and enzymatic activities of molds were analyzed during koji fermentation. In addition, the microbiological, and sensory characteristics of soy sauce were also analyzed during moromi fermentation. During the koji stage (0–72 h), the moisture content of C1 sample decreased to 20.6 ± 1.30% (p<0.05), while the pH dropped to 5.08 ± 0.00. The α-amylase activity increased significantly to 66.56 U/mL (p < 0.05). During the 32-month moromi fermentation, salt concentration decreased from 18% to 12.75 ± 0.35%, whereas reducing sugars increased to 2.93 ± 0.05 g/100 mL and total acidity declined to 2.31 ± 0.00. The lower amino nitrogen content (0.66 ± 0.03 g/100 mL) in C1 was attributed to microbial metabolism, oxidation, and Maillard reactions. For microbiology quality of soy sauce, there was no presence of yeasts and molds (TYMC) and total plate count (TPC) among all 4 conditions. The sensory evaluation revealed acceptable consumer preference for all samples, with mean scores showing only a slight difference where 6.00 ± 0.79 for C1, 6.38 ± for C3 and 6.82 ± 0.98 for C4 compared to the commercial Kbal Kor soy sauce (6.39 ± 0.87; p>0.05). These findings indicate that the experimental soy sauce possessed comparable quality to the commercial product, suggesting its potential acceptability in the consumer market.