This study systematically investigated the effect of aging temperature on microstructure, impact toughness and pitting behavior of flux-cored arc welded 2205 duplex stainless steel joint. 600°C–900°C aging treatments were carried out with 1-hour insulation. The results showed that the ferrite (α) underwent serial metallurgical transformations with increasing the aging temperature. The formation of the sigma (σ) phase was detected in the weld zone (WZ) under all aging temperatures due to eutectoid reaction of the α phase, while the peak content of the σ phase was reached at 800°C aging. A similar content variation of the σ phase was detected in the heat-affected zone (HAZ). Secondary austenite (γ2) and chi (χ) phases were only observed in the WZ and HAZ below 800°C aging. The impact toughness and the pitting resistance of the welded joints were strongly related to the σ phase content, that the 800°C aging specimen possessed the lowest impact toughness and the worst corrosion resistance due to the maximum content of the σ content in both the WZ and the HAZ.