Baan is an Ogonoid language within the Delta Cross language family of the Benue-Congo sub-phylum spoken in Tai local government area of Rivers state, Nigeria. Although Baan is a distinct language within the Ogoni group, it remains the least investigated when compared with other Ogonoid languages such as Eleme, Gokana, Kana, and Tee. This paper sets out to identify and undertake a phonetic analysis of Baan vowels. The data were elicited through personal interviews using the 1700 SIL Comparative African Wordlist. The linguistic consultants included six competent native speakers of Baan, within the age bracket of 35 – 60. Acoustic vowel qualities of formant one (F1) and formant two (F2) values were measured and analyzed using the Praat software, while the phonetic transcription was done with careful and multiple playbacks of the recorded sounds collected with the aid of Wavepad and Audacity audio recording and editing software. The phonemic analysis was done using the principle of minimal pair contrast. The findings revealed that like other Ogonoid languages, Baan records seven oral vowel phonemes /i e ɛ ɑ ɔ o u/ and five nasal counterparts /ĩ ɛ̃ ɑ̃ ɔ̃ ũ/. Both oral and nasal vowels have long counterparts. Contrasts were established between the short and long vowels, and between the oral and nasal vowels. Furthermore, acoustic analyses ascertained /i e ɛ/ as front vowels, /u o ɔ ɑ/ as back vowels, and the approximate duration of long vowels as almost twice that of short vowels. Contrary to earlier studies that the vowel [a] is a front vowel in Ogonoid, the present study revealed that it is a back vowel in Baan /ɑ/.