The repair of corroded reinforced concrete (RC) structures is necessary to improve their serviceability. Ultra-high toughness cementitious composite (UHTCC), characterised by excellent tensile behaviour, crack control capacity, and durability, shows great potential for the repair and strengthening of corroded members, especially in harsh marine environments. This paper presents an experimental study and a theoretical analysis of the flexural performance of corroded RC beams repaired with UHTCC. The experimental results indicated that macro cracks in concrete were transformed into multiple fine cracks and a slight nonlinear strain distribution was observed along the sectional depth. The replacement of damaged concrete with UHTCC can recover the initial load-carrying capacity at corrosion ratios within 11.2%. After yielding of beams, the development of UHTCC-concrete interface crack in the pure bending region was beneficial to ductility improvement. A theoretical model considering the effect of pitting corrosion was proposed for calculating flexural capacity of repaired beams.