Della Casa appeared in Britain for the first time singing the part of Countess Almaviva in Mozart's "Le nozze di Figaro" at the Glyndebourne Festival. She sang the part of Arabella for the first time at the Bavarian State Opera House in Munich in 1951. She was to become most famous for this role. She sang Eva in Wagner's "Die Meistersinger von Nürnberg" at the Bayreuth Festival in 1952, but she did not like the atmosphere there with all the arguments, so she never returned to Bayreuth. From 1953 to 1968 she sang regularly at the Metropolitan Opera House in New York where she was extremely popular.