Provided are an interconnect board (ICB) assembly suitable for a battery module of horizontal stack structure including unidirectional battery cells stacked with cell leads facing each other, a battery module comprising the same and a method for fabricating the battery module. The ICB assembly according to the present disclosure includes an ICB frame in which cell leads of unidirectional battery cells are received such that the unidirectional battery cells having the cell leads at one end are placed facing each other with the cell leads facing each other, and busbars assembled in the ICB frame and electrically connected to the cell leads.