This chapter is an investigation of vowel hiatus at the root-suffix boundary in Spoken Persian. While some languages either allow hiatus or ban it, Persian falls within the lesser-investigated category of languages that both allows hiatus and resolves it through different strategies. One of the goals of this research is to show that when vowel-final roots host vowel-initial suffixes, three main variants regarding tolerance and resolution of hiatus are possible in Persian: (1) vowel hiatus can be preserved, (2) suffix vowel can be elided to avoid hiatus, and (3) consonants can be inserted intervocalically to resolve hiatus. Importantly, it is aimed to show that there are a number of factors that systematically motivate or ban the realization of each of these variants and hence shape the hiatus pattern in this variety of Persian. These factors include phonological constraints, suffix length, and importantly the morphosyntactic properties of the suffixes that override the role of the other factors. The central objective of this paper is to show that in order to account for certain variable realizations (such as the hiatus pattern in Spoken Persian) at morpheme boundaries, it is required to consider the role of multiple factors, including the role and function of morphosyntactic elements.