Hans John was born in Ziegenhain, Hesse, and studied law at the University of Berlin. In 1939, he was hired as a legal assistant at the Aviation Law Institute in Berlin. In June 1940, he was instated into the Wehrmacht, but after suffering a wound at the Eastern Front, he was released back into academics.
With his brother Otto, John was in contact with the resistance elements within the Abwehr and Oberkommando der Wehrmacht. After hearing about Operation Walküre, the brothers joined the resistance, and became heavily involved in the July 20 Plot to kill Hitler. After Hans Oster and Hans von Dohnanyi were arrested in the spring of 1943, they kept the escaped Ludwig Gehre hiding from the Gestapo.
John was arrested in August 1944 on plotting charges, and was severely mistreated in jail. The People's Court sentenced him to death in February 1945. He was shot in April 1945 by a Sonderkommando, near Berlin's RSHA office. His brother Otto managed to escape Germany in July 1944.