As the first study reported in the literature on the axial behavior of noncircular high-performance fiber-reinforced cementitious composite (HPFRCC) members externally jacketed by fiber-reinforced polymer (FRP) sheets, the aim of this paper is to experimentally identify the axial behavior characteristics of these members under compression. The test results of 21 specimens showed that the axial and lateral deformation characteristics of FRP-jacketed HPFRCC members are significantly different from those of FRP-confined conventional concrete members. Small voids in HPFRCCs due to the presence of fine aggregates and reduced crack widths due to the contribution of steel fibers limit the transverse deformations remarkably until the axial strain value is approximately 0.0035. The test results show that the dilation ratio increases after the axial strain reaches this value. Then, the external FRP jacket begins to noticeably affect the behavior, resulting in a significant improvement in the axial strength and deformation capacity. However, since the external FRP jacket is activated after relatively large axial strains, significant strength degradations can occur before the FRP jacket provides an effective contribution. As the stiffness of the FRP jacket increases, the strength degradation experienced before the activation of the FRP jacket decreases. Furthermore, the predictions of five available models that were developed for modeling the axial behavior of FRP-confined concrete are examined through comparisons with test results.