A novel technique to improve the effectiveness of fiber-reinforced polymer (FRP) confinement for strengthening rectangular reinforced concrete (RC) columns is to implement section curvilinearization (SC) before FRP wrapping. In this SC technique, the four flat sides of a rectangular column are transformed into slightly curved sides, which increases the sectional size only slightly but can significantly enhance the FRP confinement effectiveness. However, existing research on curvilinearized square/rectangular columns (CSCs or CRCs) (particularly on CRCs) is very limited and has been conducted using small-scale specimens. To this end, the first-ever experimental program of axial compression tests on large-scale FRP-confined CRCs was recently carried out, and the results are presented in this paper. The experimental program covered the rise-to-span ratio of the curved sides, the corner radius ratio, and the sectional aspect ratio as the key test variables. The experimental results show that the slope of the linear second segment of the stress–strain curve of FRP-confined concrete in a CRC is much larger than that of the corresponding column without SC, demonstrating the effectiveness of the SC technique. On the basis of the present test results, an evaluation of the accuracy of the only stress–strain model for FRP-confined concrete in CRCs available at the time of conducting the present study is reported.