Parpola's research and teaching interests fall within the following topics:
Indus Civilization / Indus script and religion / Corpus of Indus Seals and Inscriptions
Veda / Vedic ritual / Samaveda / Jaiminiya Samaveda texts and rituals / Purva-Mimamsa
South Asian religions / Hinduism / Saiva and Sakta tradition / Goddess Durga
South India / Kerala / Tamil Nadu / Karnataka
Sanskrit / Malayalam / Kannada / Tamil / Prehistory of Indian languages
Prehistoric archaeology of South Asia and (in broad sense) Central Asia / Coming of the Aryans
Two significant contributions of Parpola, to the field of decipherment of the Indus script, are the creation of the now universally used classification of Indus valley seals, and the proposed, and much-debated, decipherment of the language of the script.