Concrete-filled tubes (CFT) are economical and easy to fabricate. As the cross-sections of CFTs are small, the interface shear between steel tube and concrete can be transferred by direct bond. As the cross-sectional dimension increases, shear connectors may be required to transfer the interface shear. However, welding shear connectors inside the steel tube is difficult. In this study, a new type of shear connector that could be installed from outside the steel tube was developed. A pilot test on five specimens demonstrated that the corner shear connector, which is a steel plate located at the corner of a square steel tube, at a 45° angle to the tube wall, is much superior to shear studs in terms of transferring the interfacial shear force. Furthermore, push-out tests of 18 CFT specimens were performed to investigate the strength and the behavior of the corner shear connectors. The strength of the specimens is found to be independent of the cross-sectional area of the shear connector. Instead, the jointed bearing area, which is defined as the cross-sectional area of the shear connection combining the area enclosed by the shear connector and the steel tube, is the major parameter that is closely correlated with the strength of the specimens. Furthermore, the ultimate strength of the specimens is positively correlated with the bearing distance, which is the distance between the loading point and the bearing surface of the connector. In addition, the strength of the corner shear connectors, which have a total jointed bearing area equaling 10.8% of the total concrete area in the steel tube, can adequately satisfy the strictest requirement for the shear transfer.