Current design codes do not deal with bridge fires despite their catastrophic consequences, especially when the bridge deck is built with steel I-girders. The most advanced approach to study the fire response of a bridge is the use of Computational Fluid Dynamics (CFD) models to simulate the fire scenarios coupled with FE thermo-mechanical models. In the case of steel girder bridges, FE models usually include a single girder and not the full deck to make the analyses required much simpler and less time consuming. In this paper, the validity of this assumption is verified. To reach this goal, the fire response of a steel girder bridge spanning 21.34 m is obtained using single girder and full deck FE models. Results show that single girder models can reasonably predict the failure time and failure mode of the most damaged bridge girder, although their estimation of the final deflections are not so good.