Fatigue and corrosion damage are the major concerns of automotive adhesive joints, yet literature reports few works about the in situ fatigue durability of adhesive joints in corrosive environment. This study presents an investigation on the fatigue durability of automotive adhesive single lap joints by an in situ corrosion fatigue test. The joints were manufactured with commercial coated AA5754-O aluminum sheets bonded by a toughened epoxy structural adhesive. An in situ corrosion chamber was designed and employed to simulate a humid and corrosive environment by spraying 5% saline solution or distilled water mist around the joints' overlap area during fatigue testing. The test results show that in the 5% saline solution mist environment, the joints' fatigue lives encountered a great loss for about an order in magnitude compared to the joints tested in laboratory environment. The difference of fatigue lives between 5% saline solution mist test and distilled water mist test is insignificant. The fracture surface analysis by scanning electron microscope and EDX techniques indicates that the adhesive joints failed interfacially in the corrosive environment, which differs from the cohesive failure mode in the laboratory environment.