The effective transfer of the shear forces along with limiting the slippage to achieve appropriate composite behavior is the most important issue associated with steel–concrete joints. Therefore, shear connectors are widely used as force transfer devices in the steel–concrete interface in the joint area. Rigid shear connectors having high strength and stiffness, and small dimensions are a good suggestion to be used in the joint area of composite structures where a high level of shear stresses is transferred in a limited space. To clarify shear behavior of rigid shear connectors in the confined condition of the joint area, six specimens were put under push-out testing. Furthermore, the mechanical properties of the shear connectors were investigated through finite element modeling. The load–displacement graph of the specimens indicated that rigid shear connectors are able to transfer a high level of forces with small slippage and without resistance-decline up to relative displacement of 20 mm. The ductile failure mode occurred with the formation of the wedge-shaped rupture in the concrete in all specimens due to the confinement provided by the steel box. Experimental results showed that the shear capacity of the encased shear connectors was underestimated using Eurocode formulation.