This paper presents the design and construction of the Aiguillon railway bridge in Switzerland, one of the first railway bridges completely made of Ultra-High-Performance Fiber-Reinforced Cementitious Composite (UHPFRC). The length and width of the trough girder are respectively 6.6 m and 5.7 m. It is designed for a narrow-gauge track and two walkways. The trough is composed of two prefabricated elements in UHPFRC with steel reinforcement bars. These elements are first built in the plant and then are assembled on site by a longitudinal cast-in-place joint. The challenges and the experiences in this project are discussed and analysed in view of future projects. Furthermore, the full-scale suitability tests to validate the joint between the two prefabricated elements are described. The test results of the structural resistance of the joints are in good agreement with analytical results.