Welding is a common method for repairing damaged ship propellers, especially by cavitation erosion. Reports on cavitation erosion and corrosion behavior of copper-manganese-aluminum (CMA) alloy weldment are sparse. In this paper, CMA weldment was prepared by tungsten inert gas welding (TIG), and its cavitation erosion behavior and corrosion behavior in 3.5% NaCl aqueous solution were studied by magnetostrictive vibratory device for cavitation erosion and electrochemical device, respectively. Results show that the weld zone (WZ) of the weldment exhibits better cavitation erosion and corrosion resistance than the heat-affected zone (HAZ) and the base metal. The cumulative mass loss of the WZ is only 1/4 that of the base metal. SEM analysis of eroded specimens reveals that the base metal is attacked most severely; the HAZ less and the WZ least. The microcracks causing cavitation damage initiate at the phase boundaries. Among the three zones of the weldment, the WZ is the noblest, its corrosion potential is -266 mV, while the HAZ, -284 mV, and the base metal, -279 mV, in about 60 h exposure to 3.5% NaCl aqueous solution. And its corrosion current density is the lowest, about 0.035 A m -2 , while the HAZ, 0.078 A m -2 , and the base metal, ±0.79 A m -2 .