The mechanical behavior of the steel–concrete joints in a composite bridge was investigated. Pull-out tests on eight specimens were carried out to evaluate the connection performance of Perfobond rib shear connectors (PBL shear connectors). In addition, static load tests were conducted on three composite joint specimens with a scale of 1/2 in a composite truss bridge. The crack load, load–displacement curves, strain distribution, and the joint stiffness were obtained from the composite joint to analyze the mechanical behavior of steel–concrete joints. The experimental results show that the embedded depth plays an important role in the ultimate bearing capacity and the deformation of PBL shear connectors and could even change the failure mode. Based on the test results of composite joints, the displacement increased almost linearly with the horizontal load on the concrete chord. There was no evident failure, and large deformation occurred in composite joints. In addition, the ultimate loads obtained from three composite joint specimens were greater than 2.93 times the design load (2050 kN). These investigated composite joints had excellent bearing capacity (above 6000 kN). This study will provide an experimental reference for the design of steel–concrete joints for composite truss bridges.