Harald Poelchau grew up in Silesia; his father was a pastor. He studied theology and social work. He married Dorothee Ziegele in 1938 and lived with her in Berlin, where their son Harald Stephan was born.
In April 1933 Poelchau began work as a prison chaplain in Berlin-Tegel, and later in other prisons including Plötzensee. He was a determined opponent of National Socialism. As a prison chaplain, he ministered to many prisoners sentenced to death by the National Socialists. He used his work to provide prisoners secretly with food and pass on messages to their relatives and fellow prisoners.
From 1941 he helped Jews to go into hiding. He and his wife took persecuted people into their home, found hiding places, and arranged forged papers. He was supported not only by Dorothee Poelchau and his longstanding partner Gertie Siemsen, but also by his large circle of acquaintances. Poelchau was also in contact with the “Uncle Emil” resistance group, and joined the Kreisau Circle in 1941.
Harald Poelchau was honored as Righteous Among the Nations on November 30, 1971.