Johannes Mannov was born in Copenhagen and received his very first singing training in the famous Copenhagen Boys' Choir. After a year of studies with Kirsten Buhl Møller he was admitted to the Musikhochschule in Freiburg and later in Karlsruhe, where he studied in 1981-88. In 1987-90 Johannes Mannov was a member of the ensemble of the Kassel Staatstheater. Engagements as an oratorio soloist in this period included Haydns Creation with the Berlin Radio Symphony Orchestra and Frans Brüggen. In 1990 he sang Christ in the St. John Passion at the Barbican Hall with Sir George Malcolm and the English Chamber Orchestra. In 1991 Mannov guested at the Northern Ireland Opera and sang Count Almaviva in The Marriage of Figaro and Guglielmo in Cosi fan tutte. The following year he toured Europe with La Chapelle Royale and Philippe Herreweghe in the role of Christ in the St. Matthew Passion. He also sang in the St. John Passion at the Tivoli Concert Hall in Copenhagen with Peter Schreier conducting. At the Innsbruck Opera in 1992 he made his debut in the title role of Don Giovanni, a role he has also sung in Northern Ireland and Darmstadt. He has been a member of the ensemble in Innsbruck since 1992. The same year he made his first appearance at La Monnaie in Un ballo in maschera and was invited back to sing Ned Keene in Peter Grimes in 1994.