After the Anschluss, he was appointed "Landeshauptmann" of Upper Austria on 14 March 1938. On 10 April he was elected as a member of the German "Reichstag", representing Austria. On 1 June 1938, Eigruber joined the SA, with the rank of SA-"Brigadeführer" effective 12 March. On 25 July, he also joined the SS as a "Standartenführer" also with an effective date of 12 March. On 22 May Adolf Hitler appointed him "Gauleiter" of Reichsgau Oberdonau. He thus united under his control the highest party and governmental offices in his jurisdiction.