Theo Lingen was born the son of a lawyer in the city of Hanover, and grew up there. He attended the Royal Goethe Gymnasium – the predecessor of the Goethe School – in Hanover, but left before taking the Abitur (final exams). His theatrical talent was discovered during rehearsals for a school performance at the Schauburg boulevard theatre. Beginning his professional stage career, the young actor adopted as a stage name his middle name together with that of the birthplace of his father, Lingen in the North German Emsland region. As “Theo Lingen” he performed at theatres at Hanover, Halberstadt, Münster and Frankfurt; in plays like The Importance of Being Earnest he very quickly earned a reputation as a superb character comedian, distinguished by his characteristic nasal speech. This distinction followed him when he began appearing in films in 1929, often together with the mumbling Viennese actor Hans Moser, since together they made a contrasting pair. In 1929 he was invited by Bertolt Brecht to the Theater am Schiffbauerdamm in Berlin, where he performed as Macheath in The Threepenny Opera. He starred in drama films like M and The Testament of Dr. Mabuse directed by Fritz Lang. In February 1928, Theo Lingen’s daughter, Ursula, was born to Bertold Brecht’s then wife Marianne Zoff (1893–1984). Brecht and Zoff divorced in September; Lingen and Zoff married later the same year, they also raised Zoff’s elder daughter Hanne. Conditions worsened after the Machtergreifung of 30 January 1933: Because Zoff was of Jewish descent, which under the Nazi regime usually resulted in a professional disqualification (Berufsverbot), Lingen thought about going into exile. However, because of his great popularity with the general public he was given a special permit by Propaganda Minister Joseph Goebbels to continue to perform and was able to protect his wife from persecution. In 1936 Gustaf Gründgens placed Lingen at the ensemble of the Berlin Prussian State Theatre. He also directed films like Hauptsache glücklich (1941) starring Heinz Rühmann.

In 1944 Lingen moved to Vienna, and in view of the approaching Red Army retired to his cottage at Strobl on the Wolfgangsee shortly afterwards. Here for a few days in May 1945, he acted as de facto mayor, when he managed to disempower the local Nazi authorities and surrendered to the US Army at St. Gilgen. Lingen’s measures were followed by the liberation of King Leopold III of Belgium and his wife by the 106th Cavalry Regiment. After the war he became a naturalised Austrian citizen, and from 1948 worked as a character actor at the Vienna Burgtheater and appeared frequently onstage in Germany, most notably in Carl Sternheim satires directed by Rudolf Noelte. Foremeost however he pursued his film career, performing in numerous comedies of varied quality, in his later days of the 1970s also on television, for example as a presenter for Laurel and Hardy films. Theo Lingen died of cancer in 1978 at the age of 75 in Vienna. The city of Vienna dedicated a grave to him at the Zentralfriedhof. The municipalities of Strobl and Lingen (in 2007) have named squares in his honor.