Steel bracing has long been used for the retrofit or the upgrading of existing reinforced concrete (RC) frame buildings. When the new braces are located external to the existing frame, they form a completely new and independent structural system, sometimes called “exoskeleton”. Whatever is the topology of the new steel structure, it needs to be connected efficiently to the existing reinforced concrete frame. The calculation method accepted in Europe for steel connections is the “component method”, which schematizes the connections as an assembly of rigid bars and (elastic-plastic) springs. The typical hybrid steel-to-concrete connection is that between a steel column and a concrete foundation. For column base connections, the current Eurocode 3 provides rules for unstiffened base plates. However, when connecting a new steel exoskeleton to an existing RC frame for seismic upgrading purposes, the large values of the internal forces to be transferred between the structures, very likely lead to the need of many anchor rods and a stiffened connecting plate. Therefore, the objective of this paper is to propose and discuss a component model for hybrid steel-to-concrete connections with stiffened anchor plates. The application of the model to a few case studies are then described, and the model predictions are compared to numerical results by means of finite element models.