The article examines the phonetic constraints operating in the phonotactic system of the Persian language and the phonetic phenomena occurring in speech from a morphonological perspective. The study analyzes the distribution of phonemes within words and morphemes, syllable structure and syllable patterns, the morphonological function of stress, as well as the phonetic adaptation of borrowed words. Special attention is paid to such phonetic processes as elision, prosthesis, epenthesis, and assimilation, with an emphasis on their causes and functional outcomes. These processes are shown to play an important role in maintaining phonotactic regularity and regulating the interaction between phonetic and morphological levels of the language. The research is based on descriptive and comparative methods. The findings demonstrate that phonotactic norms and phonetic regularities in Persian are closely interconnected with morphological processes and play a significant role in the stabilization and historical development of the phonetic system of the language.