Born into a Silesian weaver family of Jewish origin he received his education at the Realschule in Vienna. Early on, he was an actor in at the Burgtheater in Vienna. Only 21 years old he became manager of the failed Bremer Stadttheater. His success in rescuing the theater not only moved the Senate of the city to pass a resolution thanking him, but also brought him to the attention of Adolf Neuendorff, who was the manager of the Germania Theatre in New York. On invitation of Neuendorff Conried moved in 1878 to New York City, where he became chief stage manager of the Germania Theatre. In 1881 he moved to the Thalia Theatre as artistic manager and in 1882 he became artistic manager of the New York Concert Company.
In 1893 he assumed the management of the Irving Place Theatre. In 1903, he succeeded Maurice Grau as director of the Metropolitan Opera (until 1908). His first season at the Met was notable through the first production of Parsifal outside of Bayreuth, against the wishes of Cosima Wagner, who went to court but failed in her attempt to forbid the production. By December 31, 1913, when the copyright of Parsifal expired, the work had been represented 43 times at the Metropolitan Opera. Enrico Caruso, who until then had refused all offers to come to America, was persuaded by Conried to come to New York and sing at the Met. Soon after he had become director of the Metropolitan Opera, he conceived the New Theatre. On May 1, 1908 he retired from the Metropolitan Opera House due to his poor health. Immediately afterwards he voyaged to Europe. He died on April 27, 1909 in the Hotel Meranerhof in the city of Meran from an apoplectic stroke in the presence of his wife and sister.