Duncan Macmillan's work has been performed throughout the world, including at the National Theatre, Royal Court, Almeida, Barbican, St Ann's Warehouse, Melbourne Theatre Company, Berliner Ensemble, Hamburg Schauspielhaus, Schauspielhaus Ko ln, Burgtheater Vienna, Vesturport, Kansallisteatteri, Nationaltheatret Oslo and in the repertory of the Schaubu hne Berlin, as well as the Edinburgh Festival, the Manchester International Festival, Salzburg Festival, Festival d'Avignon and Theatertreffen, in the West End and on Broadway. His plays include Lungs; People, Places and Things; Every Brilliant Thing; Rosmersholm (adapt. Henrik Ibsen); 1984 (adapt. George Orwell, co-written and co-directed with Robert Icke); City Of Glass (adapt. Paul Auster) and 2071 (co-written with Chris Rapley), all published by Oberon Books. Other plays include The Forbidden Zone; Wunschloses Unglu ck (adapt. Peter Handke); Reise Durch die Nacht (adapt. Friederike Mayro cker).

Both 1984 and People, Places and Things were nominated for Best New Play at the Olivier Awards.