Janko's scholarship has focused primarily upon Bronze Age Greece, archaic Greek epic, especially the Iliad of Homer, ancient literary criticism, especially the "Poetics" of Aristotle, early Greek religion and philosophy (especially Empedocles, Orphism, and the Derveni papyrus), and the reconstruction of ancient books on papyrus-rolls.
In 2008 he brought out the site-report of the excavations at the Bronze Age and Medieval settlement of Ayios Stephanos in Laconia; these excavations do much to clarify relations between Minoan Crete and the Mycenaean mainland.