Modular steel construction is a fast evolving field the practices of which leads to reduced construction time and cost compared to traditional construction procedures. The concept of modular construction is usually adopted in low to medium rise structures. But in recent years this technique is increasingly employed in high rise structures to meet the infrastructure demands of the growing cities. The importance of steel connections in these modular structures can be easily recognized as it limits the design height and functional use of the structure. Our research at the University of Windsor focuses on studying the structural behaviour of proprietary steel modular connectors and connection designs in steel modular structures. Full-scale laboratory tests aided with extensive finite element analysis is adopted to study and optimize these connections. Our research helps structural engineers to develop a design framework in steel modular construction.