Somali is well known to exhibit vowel harmony (Armstrong 1934), but linguists know remarkably little about how the system is implemented. Most presume that harmonic oppositions involve the tongue root and analyze the system relative to the feature [atr], though the phonetic implementation of the contrast is complicated by a “quirky” (Krämer 2008) vocalic system. Reports also indicate that harmonic alternations vary between speakers and dialects, including in the bounds of the harmonic domain, but again, little systematic comparison has been pursued. To better understand the bear- ing that vowel quality and vocalic contrasts have on Somali vowel harmony, this paper reports the results of a study aimed at establishing details of the Djibouti Somali vocalic system. Our findings reveal that while a harmony system seems intact for all speak- ers studied, three consistent trends of acoustic (i.e., vowel space) overlap emerge from the data which may portend eventual mergers. These trends align in notable ways, but not entirely, with reports of harmonic decay elsewhere in the literature. They suggest that loss of harmonic distinctions in high vowels may be underway, but in different ways, in front vs. back vowels and that harmonic contrasts in long vowels are partic- ularly susceptible to weakening. Our interpretation of these results, viewed alongside the typological literature on atr harmony systems, is that Somali vowel harmony may be threatened or in decline as a result of these acoustic overlaps.