Fritzsche was born in Bochum (a city in the Ruhr Area) and served in the German army in 1917. Post-war he studied briefly at a number of universities before becoming a journalist for the Hugenberg Press and then involved in the new mass media of the radio, working for the German government. In September 1932 he was made head of the Drahtloser Dienst (the wireless news service). On May 1, 1933, he joined the NSDAP.
Under Joseph Goebbels' Reich Ministry he continued to head the radio department before being promoted to the News Section at the Ministry. In mid-1938 he became deputy to Alfred Berndt at the German Press Division. Responsible for controlling German news, the agency was also called the Home or Domestic Press Division. In December 1938 he was made chief of the Home Press Division. In May 1942 Goebbels took personal control of the division, and Fritzsche returned to radio work for the Ministry as Plenipotentiary for the Political Organization of the Greater German Radio and head of the Radio Division of the Ministry.
Fritzsche was taken prisoner by Soviet soldiers in Berlin on May 2, 1945. He was sent to Moscow for interrogation at Lubyanka Prison where, according to his own account, three gold teeth were yanked from his mouth upon arrival. He was confined to a "standing coffin", a 3-foot-square cell where it was impossible to sleep, and placed on a bread and hot water diet. He eventually signed a confession.
Later, while on trial at Nuremberg, he wrote his account of Soviet prison  which was published in Switzerland.
Fritzsche was sent to Nuremberg, and tried before the International Military Tribunal. He was charged with conspiracy to commit crimes against peace, war crimes and crimes against humanity. It was unclear to attendees why he was charged, rumors abounded that he was only in the dock as a stand-in for Goebbels. William Shirer remarked that "no-one in the courtroom, including Fritzsche, seemed to know why he was there – he was too small a fry – unless it were as a ghost for Goebbels..." He was one of only three defendants to be acquitted at Nuremberg (along with Hjalmar Schacht and Franz von Papen). He was acquitted because it became evident to the tribunal that he had never pushed for the extermination of the Jews, and on two instances he even attempted to stop the publication of the anti-Semitic newspaper Der Stürmer.
He was later tried by a West German denazification court and was sentenced to nine years. He was released in September 1950 and died of cancer soon after. His wife Hildegard Fritzsche (born Springer) died the same year.