This paper assessed the service life of RC bridges subjected to carbonation under a changing climate based on time-dependent reliability analysis. First, a simplified carbonation model and the corresponding incremental method were briefly reviewed. Then, the fatigue damage prediction model and climate model were briefly introduced. Afterward, the Monte Carlo simulation-based time-dependent reliability analysis procedure for service life assessments was presented, which integrated the carbonation depth prediction model, fatigue damage prediction model and climate model. Based on the analysis procedure, a comprehensive case study was conducted to estimate the effects of climate change, fatigue damage, concrete cover thickness and concrete grade on the service life under different reliability levels. The case study showed that the service life under a reliability level of 2 is around half of that under the reliability level of 1. Under the reliability level of 1.5, the service life under RCP8.5 (a high emission scenario defined by Intergovernmental Panel on Climate Change) can be 28 years shorter than that under no climate changes. The service life at girder top undergoing compressive fatigue damage can be 49% shorter than that without fatigue damage and 25 years shorter than that at girder bottom undergoing tensile fatigue damage. The service life at girder top with a concrete cover thickness of 45 mm can reach 2.6 times that with a concrete cover thickness of 25 mm. The service life of C50 concrete can reach approximately 2–3 times that of C30 concrete. These findings inform civil engineers that for existing RC bridges, the effects of climate change and fatigue damage should be properly considered when the remaining service life of RC bridges is concerned. Moreover, for planned RC bridges, higher concrete grade and thicker concrete cover are two effective choices to achieve a longer service life.