In 1982, Rundek obtained his diploma in theatre directing from the Academy of Dramatic Arts in Zagreb with his graduation performance of America Hurray! by J.C. Van Italie. He went on to direct a number of plays (They say the Owl Once Was the Baker's Daughter; Three Slaps, Satires from Hekuba, No, Ballads of Petrica Kerempuh...), and also appeared occasionally as an actor. Darko's principal role in the theatre remains that of composer, with more than 30 productions to his credit, ranging from intimate children's theatre to international touring performances.