Although Boulez never met or corresponded with the Second Viennese composers (Schoenberg, Berg and Webern), their influence on him was palpable. He first encountered their music through René Leibowitz in 1945 and began writing about their compositions from 1948. This chapter examines Boulez’s extensive writings on the music of the Second Viennese composers as well as his programming and conducting of their works, demonstrating that he was a central figure in their post-war reception. He frequently criticises the Second Viennese composers for reliance on conventional formal structures and explains that he is most interested in compositions that display ‘ambiguities’. He extols Webern’s compositions for using ‘elements of classical language’, which through their distorted use become ‘the elements of a new language’. Treating the Second Viennese composers’ innovations as building blocks, Boulez’s compositions expand upon what he identifies as their most important attributes: serialism and the crafting of novel timbres and sonorities.