Johannes Erath studied first violin with Rainer Küchl at the University of Music and Performing Arts in Vienna and with Hansheinz Schneeberger in Freiburg. He worked as an orchestra musician at the Volksoper Wien and the Orchesterakademie of the Vienna Philharmonic Orchestra. There after he decided to go toward directing, first he served as an assistant to Willy Decker, Nicolas Brieger, Guy Josten, Peter Konwitschny and Graham Vick in theaters all over Europe.

Among the early productions of Erath were the world premiere of the world premiere of Peter Eötvös’ Paradise Reloaded, Les Contes d’Hoffmann and Cendrillon in Bern, for which he received the 2008 Götz Friedrich Preis. Further productions were Orfeo ed Euridice, Aida, Manon, Faust and L’amour de loin at the Oper Köln, La traviata and The Cunning Little Vixen at the Hamburg State Opera. A long term cooperation was established with the Oper Graz during the directorship of Elisabeth Sobotka (2009-2015). In Graz Erath directed Lulu, Don Giovanni, Elektra, Lohengrin and Die Tote Stadt. Lohengrin was transferred to Oslo Opera, Die Tote Stadt was 2015 rewarded as the best Production in Austria. Since 2009, Erath regularly works at Oper Frankfurt. He debuted with Eötvös’ opera version of Angels in America, followed by Otello, Giulio Cesare, Euryanthe, Der Mieter and Krol Roger. Nozze di Figaro was created at the Semperoper Dresden and revived at Savonnlina Festival. Les Contes d'Hoffmann opened first at the Semperoper, later at the Finnish Opera and on January 22 in Valencia. Recent productions were Un ballo in Maschera and I masnadieri at Bayerische Staatsoper, Caruso a Cuba at the National Opera Amsterdam, La Vestale at the Theater an der Wienand Make No Noise, Beatrice Cenci and Rheingold at the Bregenzer Festspiele. During the pandemic he invented an evening called "Vissi d’arte“ in Düsseldorf and "Crepuscolo dei sogni“ at the Teatro Massimo in Palermo, the opening of the season 21/22, created as a live-stream.