Concrete-filled steel tube (CFT) columns are widely used in high-rise and large-scale buildings due to their high strength and ductility. In Korea, several sectional configurations, including internally protruded and externally thickened plate types, have been developed; however, domestic fire design remains prescriptive, requiring fire protection regardless of sectional characteristics. To address the limited research on protected and unprotected CFT columns, this study conducted non-loaded and loaded fire tests on representative Korean sections and carried out sequential thermal and thermal-stress analyses to evaluate their fire behavior. Non-loaded fire tests investigated the influence of sectional shape, size, steel tube thickness, and fire protection type under a 3-hour ISO 834-1 standard fire. Loaded fire tests applied a 40% axial load ratio to examine the performance of columns protected with 16 mm SFRM and 1.9 mm intumescent coating. A two-dimensional transient heat transfer model was developed, and the predicted temperatures agreed with measurements within approximately 10%. The computed temperature histories were subsequently used as input for a finite element thermal-stress analysis incorporating temperature-dependent strength reduction factors from EC3 and EC4, with predicted deformation and failure time matching experimental results within about 10%. Results showed that larger cross-sectional sizes reduced steel tube temperatures by 7–10%, while smaller width-to-thickness ratios achieved an additional 3–4% reduction. Unprotected columns exhibited thermal expansion, load transfer, and failure, whereas SFRM-protected columns sustained continuous expansion for nearly 150 minutes without transitioning to failure.