With the increasing demand for rehabilitation of historic structures, much research has been completed on retrofitting techniques of old steel frame buildings. Many existing buildings in the United States are concrete-encased steel frame buildings designed in the early 1900s for the advantages they provide such as resistance to fire and corrosion. With age, these types of old buildings have lost their strength and need attention to function efficiently for future uses. This research has focused on nonlinear finite element analysis of a connection of an old historic building, the Syndicate Building in St. Louis, MO, to investigate the improvement in structural performance of concrete-encased steel beam-column connection. Finite element analysis is an economical tool which is used in this study to predict the moment-rotation (M-θ) relationship and load-deformation relationship of the joint before and after the application of the FRP confinement. The FRP retrofitted connection showed improvement in the load carrying capacity and moment capacity of the riveted beam-column connection compared to the plain concrete-encased model.