This paper has investigated the shear-slip behaviour of an innovative prefabricated composite shear stud (PCSS) connector and its application in the prefabricated steel–concrete composite bridges. A series of push-out tests are carried out on a total of 12 specimens, including 6 PCSS specimens and 6 conventional shear stud (CSS) specimens. Further comparison has been carried out between the test result and the data available from the literature. Based on the test, a high-resolution finite element (FE) analysis has been performed to reveal the load transfer mechanism of the PCSS connector at the component-level. After that, an advanced FE model has been established and validated by a full-scale test of the prefabricated composite bridge using the PCSS. With the FE model, the load-slip behaviour and slip distribution are investigated in details. The result highlights the enhanced shear capacity and ductility of the PCSS specimens compared with the CSS specimens, as well as the feasibility of PCSS connectors in composite bridges. Meanwhile, it is further revealed by the detailed investigation that the enhancement could be attributed to the lateral constraint on the concrete by the vertical steel plate in the PCSS. Besides, it is also found that the load-slip behaviour of composite bridges using the PCSS is influenced by the cracking at the seam between deck blocks. Consequently, abrupt changes can be found in the load-slip curve once the cracking occurs, which differs from the traditional composite bridges.