In this study, a series of two full-scale experiments were carried out to investigate the effects of welding method on the fire resistance of concrete-filled box columns (CFBCs). The column specimens were all square sections 500 × 500 mm2 in size and 4350 mm high and were filled with high-strength concrete. Specimen CP1 was fabricated by a complete penetration weld while specimen PP1 was fabricated by a partial penetration weld. The tested columns were subjected to a constant compression load throughout the test period. The applied load corresponded to 28% of the design value of the buckling resistance of the column at room temperature. Test results indicate that the fire resistance of specimen CP1 was 55 min, compared with 51 min for specimen PP1. As a result, it can be concluded that under a load level of 0.28, the effect of different welding methods on the fire resistance of CFBC was not very significant. In addition, the established numerical model was able to reasonably predict the axial deformation of the tested columns.