A founding member and chairman of the Christian People's Party of Saarland (Christliche Volkspartei or CVP), Hoffman served as Minister-President of the French Saar Protectorate from 1947 to 1955.

After the start of World War I he volunteered, fought in Ottoman Empire among others, and was awarded the Iron Crescent.

After the First World War, Johannes Hoffmann worked as a journalist at the central organ of the German Center Party in Berlin.

He then founded the New Saar Post and struggled in his articles against the National Socialist regime and against the connection of the Saarland into the German Reich.

The Luxembourg government refused him admission as a journalist, so he was only able to publish a few articles in the Luxemburger Wort.

In 1940, at the beginning of the Western campaign, he was interned by the French in Audierne, in the Finistère department (Brittany).

His aim was "to find a solution for the Saar that would contribute to the relaxation of Franco-German relations and to promote the necessary European unity" (Hoffmann).

Hoffmann died in Völklingen in 1967 and was buried in the New World Cemetery in Saarlouis — his grave is located right next to his opponent and future successor Hubert Ney.