Atanas Mladenov was born in Sofia in a family of musicians. From an early age he began to play the violin, and later, in his teens, he began to sing. He made his professional debut in "La belle Hélène", when he was a fourth-year student at the Prof. Pancho Vladigerov National Academy of Music, where he graduated with honours in the opera singing class of Prof. Niko Isakov. He specialized at the Boris Christoff Bulgarian Cultural Institute in Rome, followed by two years at the Gioachino Rossini State Conservatory in Pesaro, Italy.
In 2008, he was engaged at the opera in Stara Zagora, where he performed the role of Alfio in "Cavalleria Rusticana" by Mascagni. The following year, he sang on the stage of the Sofia Opera in "Les Contes d’Hoffmann" by Jacques Offenbach. He then took part in Mozart's "Don Giovanni" at the Augusta Trayana Summer Festival in Stara Zagora. He also performed the role of Count Almaviva in "Le Nozze di Figaro" in Cyprus.
Since 2012, he has been a soloist at the Sofia Opera, appearing on stage as Belcore in Donizetti's "L’Elisir d’Amore", Ping in Puccini's "Turandot", Albert in Massenet's "Werther", Frédéric in Delibes's "Lakmé", Zurga in Bizet's "Les Pêcheurs de Perles", Dandini in Rossini's "La Cenerentola", Borislav in Maestro Georgi Atanasov's historical opera of the same name, Onegin in Tchaikovsky's "Eugene Onegin".
He took part with great success in Wagner's epics "Götterdämmerung" (from the tetralogy "Der Ring des Nibelungen") with the role of Gunter, "Tristan and Isolde" as Curvenal and in "Parsifal" as Amfortas, for which he was highly praised by the international music critique.