Abstract In modular steel buildings, traditional architectures are separated into prefabricated room-sized volumetric units that are manufactured offsite and installed onsite. The connections between the modules are important for load transfer. Conventional inter-module connections mainly use direct plates and connect them using bolts; however, this may prove problematic for the inner connecting regions. A new type of design with beam-to-beam bolted connections is proposed in this paper; this design provides easy working access without being affected by the structural members. The static performance, hysteretic performance, skeleton curves, ductile performance, energy dissipation capacity, and stiffness degradation patterns of the joints are obtained by experiments and finite element analyses. The results showed that because of the construction between two unit joints, gaps would be formed between the upper and bottom columns, and this gap can influence the deformation patterns and distribution of bending loads at each unit joint. The weld quality at the unit joints is critical to ensure overall safety. Stiffeners can effectively increase the stiffness and load bearing capacity, but may reduce ductility performance. The deforming ability of the connection is also closely influenced by the stiffness of the floor beam column joint and ceiling beam column joint and their relative intermediate magnitudes.