Understanding the influence of particle size distribution (PSD) on the efficiency of Microbially Induced Calcium Carbonate Precipitation (MICP) is critical for optimizing its application in soil enhancement. PSD affects porosity and retention of the cementation solution, which is essential for successful calcium carbonate precipitation. However, the role of PSD remains relatively unexplored. This study examines the influence of PSD on the efficiency of MICP treatment. Fatty sand, filter sand, and a 1:1 blend of the sands were subjected to MICP treatment over 4 weeks under identical conditions. Unconfined Compressive Strength (UCS) tests, particle size distribution analysis, and specific gravity measurements were conducted to evaluate the relationship between soil properties and MICP performance. The results indicate that fatty sand (well-graded particles) achieved the highest UCS values due to efficient retention of the cementation solution and reduced porosity, with values reaching up to 241 kPa under low CFU and high feeding conditions. In contrast, mixed sand reached 125 kPa, and filter sand failed to form testable samples, indicating poor cohesion. The low cation exchange capacity (CEC) of both sands suggests that calcium carbonate precipitation depended primarily on physical retention rather than ion exchange mechanisms. These findings emphasize the importance of PSD and specific gravity (e.g., 2.698 for fatty sand vs. 2.292 for filter sand) in optimizing MICP, while chemical interactions appear negligible in soils with little cation exchange capacity.