Ultra-high-performance fiber-reinforced concrete (UHPFRC) is a relatively new construction material. In comparison with conventional high-strength concrete, UHPFRC does not usually contain coarse aggregates larger than 6–7 mm in size. This paper presents the outcomes of an experimental study of UHPFRC beams subjected to four-point loading. The effect of two parameters was studied, namely, the fiber content and the temperature of the curing water. Eight UHPFRC beams were tested, comprising six beams reinforced with rebars and two beams without rebars. Three fiber contents were investigated in this study (1, 2, and 4% in volume). The study investigated two curing temperatures of water, 20 and 90°C. The results presented in this paper include deflections, toughness energy, and moment capacity and also includes a comparison with calculations according to EC2 provisions. A minor difference was observed in the deformation and flexural behavior of beams with fiber contents of 1 and 2% (in volume). However, beams with 4% (in volume) fibers exhibited a higher flexural capacity. Only flexural failure was observed and no shear-related failure was recorded. Beams with 1% (in volume) fibers for both curing regimes had the highest peak load toughness energy. Beams reinforced with rebars and cured at 20°C had a significantly higher bending resistance.