To investigate the effects of low temperatures and carbon dioxide reinforcement on the flexural properties of steel fibre recycled concrete, this study conducted three-point bending tests on 16 sets of carbonated recycled aggregate concrete (CRAC) beams and 16 sets of recycled aggregate concrete (RAC) beams. The flexural properties of them at different low temperatures (20 ℃, 0 ℃, -30 ℃, -60 ℃) and steel fibre volume dosage (0%, 0.5%, 1.0%, 1.5%) were compared. The flexure toughness index, flexural tensile strength, and equivalent flexural strength were calculated from the macroscopic test results to assess the flexural resistance of CRAC comprehensively. Combined with scanning electron microscopy-energy spectroscopy (SEM-EDS) analysis, the microstructure and elemental content of CRAC were analysed to reveal the mechanism of carbonation and low temperatures on the macroscopic mechanical properties of CRAC. The results showed that the flexural properties of recycled aggregate concrete reinforced with CO2 were significantly improved compared to RAC. The maximum increase in flexural tensile strength and equivalent flexural strength of CRAC after low temperatures was about 61.94% and 61.38%, respectively. CO2 can react with the cement hydration products of the recycled aggregates to produce CaCO3 and silica gel, filling in the transition zone of the CRA-matrix interface, which can improve the microstructural densification of the CRAC at low temperatures. With further decrease in temperature, the effect of low temperatures on the flexural properties of CRAC was more significant due to the impact of ice crystal growth, with a maximum enhance in flexural tensile strength and equivalent flexural strength of 131.35% and 165.93%, respectively, compared to that at 20 ℃. The strength and toughness of CRAC with 1.5% steel fibre are improved best at low temperatures.