Quasi-static tensile tests in air and slow strain rate tests in a 3.5% NaCl solution were conducted in a ultra-high-strength P/M Al-Zn-Mg alloy fabricated through powder metallurgy. Attention is also paid to fatigue strength and fatigue crack growth behavior in air and in a 3.5% NaCl solution. The alloy has extremely high strength over 800 MPa. However, elongation at break remains small, at about 1.3%. The SSRT strength in a 3.5% NaCl solution decreases slightly at a very low strain rate, that is smaller than those observed in aluminum alloys sensitive to stress corrosion. This means that the crack initiation resistance to stress corrosion is superior. However, the corrosion fatigue strength becomes lower than that conducted in air, because pitting corrosion on a sample surface acts as a stress concentrator. Fatigue crack growth resistance of the alloy is inferior to conventional Al-Zn-Mg alloys fabricated by ingot metallurgy, because the fatigue fracture toughness, or ductility, of the alloy is inferior, and intergranular cracking promotes crack growth. However, no influence of 3.5% NaCl solution on corrosion fatigue crack growth is observed.