<p>Microbially induced carbonate precipitation (MICP) is an emerging ground improvement technique that can be used to improve the geotechnical properties of sandy soils. Although the enhancement effects have been widely investigated at laboratory benchtop scale and field scale, the MICP-treated soil responses at the particle scale are still underexplored and fundamental insight about the nature of the cementitious bonds is still limited. The precipitation pattern and crystal morphology of the deposited CaCO₃ in the soil matrix may vary and significantly affect the mechanical behavior. Knowledge about the grain–crystal interactions at the particle-scale level is required for further understanding. In this study, the discrete element method (DEM) is adopted to explore the pull-out response of a pair of MICP-treated grains subjected to tensile loading. A particle generation algorithm has been developed and implemented in the numerical model, which aims to simulate the crystal nucleation and growth process and create a wedge-shaped CaCO₃ crystal near the grain contacts that forms a cementitious bond between the two grains. The numerical approach was validated based on the particle-scale experiments from the literature. Various CaCO₃ precipitation patterns are simulated, and failure characteristics are analyzed. The simulation results indicate that tensile failure can occur in both debonding and internal failure modes, depending on cementation content, crystal morphology, and CaCO₃ spatial distribution. The results presented herein can also be used for element-scale DEM models to further analyze MICP-treated soil behavior.</p>