Experimental results on the fire endurance of full-scale glass fiber-reinforced polymer (GFRP) composite columns are reported in this paper. The pultruded four-cell profiles were first loaded to axial compression (uniform serviceability stress of 5 MPa) and then simultaneously subjected to an ISO834 fire from one side until ultimate failure occurred or the planned duration of fire exposure was reached. An active water cooling system was integrated into two columns to improve the fire resistance duration. The time-dependent temperature responses and lateral deflections were recorded. The latter were caused by thermal expansion and load eccentricity due to material loss on the fire side. A non-cooled reference column failed after 50 min fire exposure while the two water-cooled columns did not fail within the planned 60 and 120 min. Previously developed models were capable of predicting the time-dependent temperature responses, modulus degradation and time-to-failure.