The Department of Estonian is the largest department in the Institute. Among other topics, the research addresses the phonetics, syntax, and semantics of Modern Estonian, as well as its variation and history. It also focuses on dialects, such as Southern Estonian, Võro, and Seto.
The department compiles and manages a number of Estonian text corpora, including the Corpus of Spoken Estonian, Phonetic Corpus of Estonian Spontaneous Speech, and Estonian Dialect Corpus.
The department includes the Laboratory of Spoken and Computer Mediated Communication and the Phonetics Laboratory. It also incorporates the Centre of Academic Estonian, coordinating the teaching of academic Estonian across the entire University.