At the surface level, Niuean has a three-way distinction between vowels of the same quality: short vowels, written as <a>; double (or rearticulated) vowels, written as <aa>; and long vowels, written as <ā>. While the Polynesian literature suggests that the distinction between long and double vowels is one based on stress assignment, little evidence has been presented to support such a claim for Niuean. This paper presents a series of arguments on how best to understand the status of Niuean vowels. We argue that double and long vowels are reducible to an underlying sequence of two identical short vowels and support this analysis with two main pieces of evidence: a corpus of words in Sperlich’s dictionary of Niuean show long vowels and double vowels to be in complementary distribution; and phonetic analyses of Niuean words suggest that the phonetic difference between long and double vowels can best be captured in terms of pitch height rather than duration, a main correlate of stress.