North Australian Kriol is an English based creole spoken widely by Indigenous people in northern Australia in areas where the traditional languages are endangered or no longer spoken. This paper offers the first acoustic description of the vowel phonology of Roper Kriol, within a variety spoken at Barunga Community, east of the town of Katherine in the Northern Territory. Drawing on a new corpus for Barunga Kriol, the paper presents analyses of the short and long monophthongs, as well as the diphthongs in the spontaneous speech of young adults. The results show the durations and spectral characteristics of the vowels, including major patterns of allophony (i.e. coarticulation and context effects). This updates the phonology over the previous description from the 1970s, showing that there is an additional front low vowel phoneme in the speech of young people today, as well as a vowel length contrast. Interestingly there are points of similarity with the vowel acoustics for traditional Aboriginal languages of the region, for example in a relatively compact vowel space and in the modest trajectories of diphthongs.