This paper provides a first description of the phonetics and phonology of Idi (Pahoturi River; ISO 639-3: idi, glottocode: idii1243) as spoken by about 1,000 people in the villages of Dimsisi and Sibidiri, located in the Morehead District of Western Province, Papua New Guinea. Idi has a fairly large inventory of 21 consonant phonemes and 8 vowel phonemes. As with other languages spoken in the region, the two central vowels show a hybrid status and could be analysed as sometimes phonemic and sometimes epenthetic. Other noteworthy characteristics are the presence of vowel harmony, voiced and voiceless retroflex plosives/affricates, nasality as a “floating” feature, and coarticulated labial-velar plosives, although the latter most likely originated as loan phonemes from Nen.