The effect of two-step aging treatment on the fatigue behavior of welded AA 7020 Al. alloy was investigated. For fatigue tests to be carried out in atmospheric and seawater environments, a plane bending tester at a stress ratio of R=0 was used. Experiments in the control group were carried out with non-welded specimens at a strain rate of R= -1 in air. The gradual heat treatment (two step aging, TSA) significantly improved the fatigue and corrosion fatigue behavior of welded AA 7020 alloys. Unwelded specimens showed better fatigue properties than welded ones. In experiments in a seawater environment, pitting and exfoliation corrosion occurred on the surface. It was determined that the corrosion pits reduce the fatigue life of welded and unwelded samples. It was also observed that the corrosion sensitivity of the welded specimens increased in the heat affected zone (HAZ) and corrosion fatigue cracking occurred in these zones.