The current study examined some issues of correct phonetic articulation of polysyllabic English and Russian words while interpreting from English into Russian by multinational students studying at the Institute of Law, Peoples' Friendship University of Russia (RUDN University). The objective of this paper is to establish similarities or differences of polysyllabic lexemes and word forms in the English and Russian languages to teach law-students to pronounce them accurately while acting as mediators or interpreting in the process of professional communication and legal activities. This goal was achieved by implementing comparative analysis of some English and Russian polysyllabic words among which are compound words, closed, open and hyphened nouns, words with prefixes, compound and complex numerals, verbs with postpositive, and polysyllabic words with terminational manner of derivation. The descriptive analysis was used as a means of presenting key ideas. The methodological bases of the paper are the conceptual provisions of Russian and foreign researchers in linguistics, psycholinguistics, theoretical phonetics, theory and methods of teaching foreign languages. The practical value is in compiling mini-vocabularies of polysyllabic words by law-students with further implementation of them in projects and game based classroom activities. The findings of the current study may help to eradicate phonetic illiteracy and problems of proper articulation of polysyllabic Russian and English words when interpreting diverse range of information in the process of professional contacts. The outlined in this article data can be useful for faculty members teaching interpretation, mediation and English for special purposes to students studying languages at non-linguistic Universities.