During the Second World War he was an active supporter of the Regent, Admiral Miklós Horthy.

After the death of Pál Teleki (3 April 1941) Keresztes-Fischer became acting Prime Minister on that day.

[2] He joined the Bethlen-Kállay political conservatives, which wanted to establish contacts with the Allies to negotiate Hungary's treatment after the war.

After the March 1944 occupation of Hungary by Nazi Germany, he was imprisoned in a concentration camp and then exiled to Austria.

His younger brother was Lajos Keresztes-Fischer, a Hungarian military officer who served as Chief of General Staff in 1938.