Hexagonal boron nitride (hBN) is widely used to develop lightweight nanocomposites for structural purposes because of its exceptional mechanical properties. Understanding the mechanical properties of hBN is essential for developing these nanocomposites, as these properties are greatly affected by atomic defects that naturally occur during synthesis. In this study, we conducted molecular dynamics simulations using a more precise reactive force field to explore the tensile strength of monocrystalline and bicrystalline hBN configurations. Our simulations revealed that in bicrystalline hBN configurations, the tensile strength decreased by 20% compared to monocrystalline configurations when the loading was perpendicular to the grain boundary (GB). This perpendicular loading caused an opening mode of fracture against the GB, resulting in early fracture. On the other hand, when the loading was parallel to the GB, it created a sliding mode of fracture against the GB, preserving the tensile strength of hBN. This comprehensive study on the tensile strength of monocrystalline and bicrystalline hBN is valuable for the development of nanocomposites for aircraft and railway structural applications.