Lost-Circulation Materials (LCMs) are used to control and mitigate fluid loss problems by fracture sealing. Without a proper lost-circulation technique, an increase in non-productive time (NPT) and well control problems may occur. A good design in the LCMs to seal fractures and to successfully prevent the occurrence of a serious lost-circulation event can alleviate a heavy drilling budget. Various LCMs exist in the market, of which can be broadly categorized as fibrous, flaky, or granular. Granular LCMs are effective in sealing fractures and are of low cost. A successful bridging and sealing from the LCMs depend on their mechanical strengths, shapes, sizes, and particularly, the particle size distribution (PSD). In this paper, the computational fluid dynamics (CFD) and the discrete element method (DEM) are coupled to simulate the sealing capabilities of granular LCMs on different PSDs. A single smoothed fracture is created for the study of such phenomenon. The dynamic process of fracture sealing involves the initiation of bridging from large particles and the effective particle packing to form a seal, thereby reducing the fluid loss. It is found that the LCMs with bimodally distributed sizes can achieve effective fracture sealing. The coarse LCMs should be close to the average fracture size, where accurate measurement is required. The median of the fine to coarse LCM sizes should not exceed 0.67 for fracture sealing to occur. The LCM blend consists of coarse and fine LCMs, where the fine to coarse LCMs by volume is around one third.