During his career, he served as the translator for Neville Chamberlain's negotiations with Adolf Hitler over the Munich Agreement, the British Declaration of War and the surrender of France.

In July 1923, Schmidt, still preparing for examinations, accepted his first assignment for the translating and interpreting service of the Foreign Office at the Permanent Court of International Justice in the Hague.

Under Reich Chancellor Gustav Stresemann, Schmidt became chief interpreter, a position he retained after Hitler came to power in 1933.

During the war years, he served as Hitler's interpreter during his meetings with Marshal Philippe Pétain and General Francisco Franco.

[4] Schmidt fails to mention the genocidal plans discussed in the Hitler-Antonescu meetings but gives the misleading impression that German-Romanian talks during the war were entirely concerned with military and economic matters.

In 1952, he founded the Sprachen & Dolmetscher Institut in Munich, a college where students could learn languages and become translators and interpreters.

Entitled An Extra on the Diplomatic Stage, Schmidt's memoirs cover his 21 years as an important eyewitness to European foreign policy.