In the Method of Characteristics (MOC) neutron transport code OpenMOC, the scattering source term is processed with an isotropic scattering approximation. However, in the actual process of neutron transport, the probability of neutron scattering in various directions is not uniform. By expanding the scattering cross-sections with Legendre polynomials and the angular flux terms with spherical harmonics, anisotropic scattering treatment under the flat source approximation is incorporated in the MOC code OpenMOC. This study selects VERA benchmark problems 1–3, which include different temperatures and burnable poison absorber rods, as well as several problems containing MOX fuel assemblies to validate the higher-order scattering functionality. Additionally, a sensitivity analysis is conducted about the impact of the number of particle histories on simulation time and keff calculation accuracy in OpenMOC. The results show that, compared to the zeroth-order approximation and the transport-corrected approximation, anisotropic scattering treatment achieves higher calculation accuracy in most cases.