Gerlich was born in Stettin, Pomerania, and grew up as the eldest of the three sons of wholesale and retail fish monger Paul Gerlich and his wife Therese. In Autumn 1889 Gerlich was enrolled in the Marienstiftungymnasium (Our Lady's Grammar School). Four years later he changed to the senior level. In 1901 he received his school leaving certificate.
In 1902 he went to study mathematics and natural sciences, then history at the University of Munich and was an active member of the Free Students. After completing his studies with a doctorate with the dissertation “The Testament of Henry VI” (1907). Gerlich became an archivist and contributed articles in an anti-socialist and national-conservative vein in the publications Süddeutsche Monatshefte and (in 1917) Die Wirklichkeit. In 1917 he also became active in the Deutsche Vaterlandspartei. (German Fatherlands Party) and 1918/19 in the Antibolschewistische Liga (Anti-Bolshevist League)
In 1919 he published the book Der Kommunismus als Lehre vom Tausendjährigen Reich (Communism as the Theory of the Thousand Year Reich), where Gerlich categorises communism as a type of redemption religion. A whole chapter is dedicated to denouncing anti-Semitism, which had gained ground because of the leading positions of many Jews in the Revolution and Soviet Republic.
During those years Gerlich’s political views become more liberal. In 1920 he was nominated as candidate to the Bavarian Landtag and German Reichstag for the left-liberal Deutsche Demokratische Partei (German Democratic Party).
On 9 October 1920 he married Sophie Botzenhart, born Stempfle, in Munich.
Editor in chief of the Münchner Neueste Nachrichten
From 1920 to 1928 he was editor in chief of the Münchner Neueste Nachrichten (MNN), a predecessor publication of today’s Süddeutsche Zeitung.
Already before 1933 Gerlich opposed Nazism and Hitler's Nazi Party as "murderous". In the early 1920s he had seen proof of Nazi tyranny already in Munich. Once a conservative and nationalist, after the 1923 Beer Hall Putsch Gerlich decisively turned against Hitler, and became one of his fiercest critics.
Friendship with Therese Neumann
In 1927 he had befriended Therese Neumann, the mystic and visionary of Konnersreuth in Bavaria, who supported Gerlich's resistance activities. Initially he wanted to expose the “swindle” of her stigmatism, but Gerlich came back as a changed man and converted from Calvinism to Catholicism in 1931. From that year until his death, his resistance became inspired by the social teachings of the Catholic Church.
Der gerade Weg
Gerlich returned in November 1929 to his job at the Bavarian National Archives. A circle of friends that had developed around Therese Neumann gave rise to the idea of founding a political weekly newspaper in order to dispute the left and right political extremism in Germany. Supported by a wealthy patron, Prince Erich Waldburg-Zeil, Gerlich was able to overtake the weekly newspaper Der Illustrierte Sonntag, which was renamed Der gerade Weg (the straight path) in 1932.
In his newspaper Gerlich fought against Communism, National Socialism and anti-Semitism. The dispute with the growing Nazi movement became the central focus of Gerlich and his writing. At the end of 1932 the circulation was over 40,000 readers.
Gerlich once wrote “National Socialism means: Enmity with neighbouring nations, tyranny internally, civil war, world war, lies, hatred, fratricide and boundless want”. (Der gerade Weg, 31 July 1932).
Arrest and death in the Dachau concentration camp
After the Nazis seized power in Germany on January 30, 1933, they quickly decided to remove Gerlich. He was arrested on March 9, 1933 and brought to the Dachau concentration camp, where he was murdered on June 30, 1934 during the Night of the Long Knives.
He was portrayed in the TV movie Hitler: The Rise of Evil by actor Matthew Modine. In the film, as he dictates a front page article that warns of the danger that Hitler poses, Gerlich finishes with "the worst thing we can do, the absolute worst, is to do nothing." This line is inspired by a quote often incorrectly attributed to Edmund Burke: "The only thing necessary for the triumph of evil is for good men to do nothing."