In 1914, right after his Abitur, he took part in the First World War as a volunteer, and was wounded repeatedly.
After the horror of his wartime experiences, Haubach resumed studying.
From 1919 to 1923, he studied philosophy, sociology, and economics and eventually graduated.
As of 1920, Haubach, like his friend Carlo Mierendorff, was an SPD member and worked together actively with the Young Socialists.
From 1924 to 1929 he was editor of the newspaper Hamburger Echo, and later (1929-1933) an associate at the Reich Interior Ministry and with the Berlin Police President.
After his first arrest in 1934, he was detained in Esterwegen concentration camp.
From 1935, he worked as an insurance representative, and later established contacts with the Kreisau Circle.
After the failed attempt on Hitler's life at the Wolf's Lair in East Prussia on 20 July 1944, Haubach was arrested and sentenced to death by the Nazi "People's Court" (Volksgerichtshof).
Now very ill, Theodor Haubach was put to death on 23 January 1945 along with Helmuth James Graf von Moltke at Plötzensee Prison in Berlin.