Abstract: This study addresses the issue of lexical borrowing in Yomut dialect of Turkmen spoken in Iran. Turkmen language is subject to alterations, as a result of contact with Persian, resulting in additions to its linguistic and mainly lexical, inventory in the form of loanwords. This study aims at investigating the nature of Persian lexical loanwords in the speech of native Turkmen speakers as well as the effect of sociolinguistic factors such as sex, education, age and local residence on the rate of borrowing from Persian. The results indicated that nouns, verbs and adjectives make up the first, second and third category of words borrowed, respectively. Also, of these sociolinguistic variables, education, age and place of residence had significant impacts on borrowing.