Walter Schellenberg was born in Saarbrücken, Germany, but moved with his family to Luxembourg when the French occupation of the Saarland after the First World War triggered an economic crisis in the Weimar Republic.
Schellenberg returned to Germany to attend university, first at the University of Marburg and then, in 1929, at the University of Bonn. He initially studied medicine, but soon switched to law. After graduating he joined the SS in May 1933 and worked in counter-intelligence. He met Reinhard Heydrich and from 1939 to 1942 was Heinrich Himmler's personal aide and a deputy leader of the Reich Central Security Office. In addition Himmler bestowed upon Schellenberg a unique position beyond that of a simple aide, making him his special-plenipotentiary (Sonderbevollmächtigter). Since Himmler held the position of general plenipotentiary to the whole Reichs administration (Generalbevollmächtigter für die Verwaltung), this effectively gave Schellenberg enormous influence within Nazi Germany.
In 1940 he was sent to Portugal to intercept the Duke and Duchess of Windsor and try to persuade them to work for Germany. The mission was a failure; Schellenberg managed only to delay their baggage for a few hours.
By the time he led the hunt for the Soviet spy ring Red Orchestra, Schellenberg had become a Major-General (Brigadeführer) in the Waffen-SS. Schellenberg had been involved in planning operations in neutral Ireland including Operation Osprey, a plan involving No.1 SS Special Service Troop. According to his memoirs, he was a friend of Wilhelm Canaris, the head of the Abwehr, whom he replaced in 1944.
At the end of the War Schellenberg persuaded Himmler to try negotiating with the Western Allies through Count Folke Bernadotte and personally went to Stockholm in April 1945 to arrange their meeting. He was in Denmark attempting to arrange his own surrender when Allied troops arrested him in June 1945.