With the continuous improvement of its research capabilities, the University of the Immaculate Conception (UIC) is taking a step higher in the advancement of its tools for research, specifically the implementation of the Open Journal System (OJS). This system allows UIC to have its research journals be published online, indexed, and able to comply with international standards. Although OJS is a free and open source tool that is readily implementable, it still needs for customization to match the university’s LW3 system to ensure the consistency of user records and avoid redundancy of data between the two systems. This action research was undertaken to custom-fit OJS for UIC for proper implementation. It followed the Rational Unified Process (RUP) in the customization process which is a proven process model created by IBM. Its stages involved Inception, Elaboration, Construction, and Transition. In the elaboration stage, an analysis of the structure of OJS was made where classes in the Model-View-Controller (MVC) architecture of OJS were identified to have the need for modifications. This was developed in the construction stage. A series of testing was done in the transition stage. Despite the difficulties encountered in matching LW3 and OJS, it was still successfully integrated in the system.