The vowel systems of five selected Iranian Balochi dialects are investigated in this study, which is the first work to apply empirical acoustic analysis to a large body of recorded data on the vowel inventories of different Balochi dialects spoken in Iran. The selected dialects are spoken in the five regions of Sistan (SI), Saravan (SA), Khash (KH), Iranshahr (IR), and Chabahar (CH) located in the province Sistan and Baluchestan in southeast Iran. The aim of the present fieldwork-based survey is to study how similar the vowel systems of these dialects are to the Common Balochi vowel system (i, iː, u, uː, a, aː, eː, oː), which is represented as the vowel inventory for the Balochi dialects in general, as well as how similar these dialects are to one another.  The investigation shows that length is contrastive in these dialects, although the durational dif-ferences between the long and short counterparts are quite small in some dialects. The study also reveals that there are some differences between the vowel systems of these dialects and the Com-mon Balochi sound inventory. The Common Balochi short /i/ vowel is modified to short /e/ in these dialects, and a strong tendency for the long /eː/ and /oː/ to become the diphthongs ie and ue, respec-tively, is observed in some of the investigated dialects, specifically in KH, which shows heavier diphthongization than the other dialects. It is also observed, especially in SI, SA, and CH, that the short /u/ shows strong tendencies to shift towards a lower position of an [o] vowel. In SI and SA, this shift seems to be a correlate of syllable structure, with lowering occurring mostly in closed syllables. It is possible that Persian, as the dominant language in the area, has had an influence on these dialects and caused a lowering tendency among the higher vowels.  The vowel systems in these dialects differ slightly from each other. Phonemically, the pairs e/eː, a/aː, u/uː, and the long vowels /iː/ and /oː/ are suggested for IR; the pairs a/aː, u/uː, the short /e/ and the long /iː/ as well as the diphthongs /ie/ and /ue/ substituted for the long /eː/ and /oː/, respectively, are suggested for KH; and finally the pairs e/eː, a/aː, o/oː, and the long vowels /iː/ and /uː/, which make a more symmetrical inventory, are suggested for the SI, SA, and CH dialects. In general, the vowels in these dialects show a range of phonetic variations. In addition, processes of fronting, which is most common in coronal contexts, and nasalization, which mostly occurs in nasal envi-ronments, are observed in the data researched.