Although the pearlitic steel is one of the most extensively studied materials, there are still questions unanswered about the interface in the lamellar structure. In particular, to deepen the understanding of the mechanical behavior of pearlitic steel with fine lamellar structure, it is essential to reveal the structure-property relationship of the ferrite/cementite interface. In this study, we analyzed the in-plane shear deformation of the ferrite/cementite interface using atomistic simulation combined with extended atomically informed Frank-Bilby method and disregistry analyses. In the atomistic simulation, we applied in-plane shear stress along twelve different directions to the ferrite/cementite bilayer for Isaichev, Near Bagaryatsky and Near Pitsch-Petch orientation relationship, respectively. The simulation results reveal that Isaichev and Near Bagaryatsky orientations show dislocation-mediated plasticity except two directions, while Near Pitsch-Petch orientation shows mode II (in-plane shear) fracture at the ferrite/cementite interface along all directions. Based on the extended atomically informed Frank-Bilby and disregistry analysis results, we conclude that the in-plane shear behavior of the ferrite/cementite interface is governed by the magnitude of Burgers vector and core-width of misfit dislocations.