Disclosed is a jamb assembly for a door having a novel structure, capable of representing a wooden feel and reinforcing the strength for a specific region by improving the structure of the jamb assembly coupled with an opening of a wall surface for the installation of the door. The jamb assembly is installed along an inner peripheral surface of an opening of a wall surface for installation of a door and constituting a door frame. The jamb assembly includes an outer skin section constituting an outer portion of the jamb assembly and having a surface molded with various patterns such as a wooden pattern, and a body core section surrounded by the outer skin section, constituting an inner frame portion of the jamb assembly, and fixedly coupled with the opening of the wall surface for the installation of the door.