In this paper, the contrastive role of the glottal stop is challenged, and its perceptual function is analyzed within the framework of Optimality Theory. The glottal stop plays a dual and complex role in the phonological and perceptual system of Persian. At the production level, it often surfaces as a marker for the onset of words that begin with a vowel, particularly in formal or emphatic contexts. From a perceptual standpoint, Persian listeners implicitly perceive the presence of the glottal stop, even in the absence of clear physical articulation, and interpret it as a cue for syllable boundary or word onset. This phenomenon indicates that the glottal stop holds a salient perceptual function in Persian. Within the framework of Optimality Theory, the insertion of a glottal stop, being the least sonorous consonant in the sonority hierarchy, creates the greatest perceptual contrast with a word-initial vowel and thus serves as a clear boundary marker for syllables or lexical items. In contrast, when an empty onset occurs between two vowels, a palatal glide /j/ is often inserted. As the most sonorous of the consonants, /j/ facilitates the smoothing of the sonority contour within the word. Ultimately, the findings of this study highlight that the interaction between production, perception, and syllable structure in Persian not only supports the integrity of the phonological system but also enhances fluent and accurate speech processing for the listener.