Fibre-reinforced polymer (FRP) jackets have been widely used to confine concrete columns to enhance their load-carrying capacity and ductility. More recently, the use of FRP jackets to improve the performance of hollow steel tubes and concrete-filled steel tubes has also been explored. This paper presents the results of a recent experimental study in which the behaviour of FRP-confined circular concrete-filled thin steel tubes under axial compression was examined. The experimental study included three series of tests and was focussed on the effects of the diameter-to-thickness ratio of the steel tube and the confinement stiffness of the FRP jacket. The test results revealed that the FRP jacket either substantially delayed or completely suppressed the local buckling failure mode of the steel tube. As a result, the compressive behaviour of the concrete-filled thin steel tube as well as the concrete is significantly improved in terms of both strength and ductility.