In the present study the effect of welding processing parameters on the corrosion and environment-assisted cracking (EAC) of 6061 aluminum alloy joints, produced by Friction Stir Welding, was studied. Different samples produced by employing rotating speeds of 630, 1000 and 1250, welding speeds of 40, 80 and 125 mm/mi and shoulder diameter of 15,18 and 21 millimeter were used. The microstructural analysis was carried out by optical microscope. The fracture surfaces of the tested specimens were examined using optical and scanning electron microscopes. using polarization tests, corrosion behavior of specimens, were studied in 3.5% NaCl aqueous solution. The polarization tests were conducted at a scan rate of 1 mV/s, using the SCE as reference and platinum as counter electrode. Corrosion rate was also determined by immersion test method, in the solution of 3.5% NaCl. EAC behavior was investigated in acidic chloride solutions, using a slow strain rate testing technique. The resistance to EAC was determined by to the percent change in tensile elongation while exposured to solution with respect to the reference environment (air). results indicated that the rotation speed (in fixed shoulder diameter and travel speed) has a major influence on corrosion rate. This is attributed to the breaking down and dissolution of the second phase particles due to the heat generation and mechanical work during stirring. Localized galvanic cells formed between the Al matrix and the second phase particles are believed to be the main reason for corrosion of FSW alloy. Dissolution of the precipitates decrease the sites for galvanic coupling and hence increase the corrosion resistance. Regarding the shoulder diameters, 18 millimeter showed the most corrosion resistance and the most noble corrosion potential. Slow rotation speed with high travel speed and high rotation speed with slow travel speed deteriorated corrosion behavior. The former condition produces coarse particles, because low heat input and low mechanical stir, while in the latter condition excessive heat input and turbulent stir produce the same particles. EAC was observed in samples welded using these parameters. EAC susceptibility is believed to be based on hydrogen embrittlement. It was demonstrated that stress corrosion cracks occur only locally in the boundary region between the dynamically recrystallized zone (DXZ) and the thermomechanically affected zone (TMAZ) regions. Results indicated that participation of low strength properties and high electrochemical activity are the main reason for EAC. Hydrogen is produced by surface corrosion reactions and part of it is absorbed in atomic form into the material, accelerating this process by localized strain produced. Results of fractographic analysis of tensile specimens indicated a quasicleavage (embrittled) zone, appearing between intergranular corrosion and ductile uncorroded area. This observation is consistent with the existence of a hydrogen affected zone, which degrades the ductility of the material. Keywords: corrosion, stress corrosion cracking, hydrogen embrittlement, slow strain rate test, AA6061-T6, friction stir welding.