The article deals with several similarities that are reveled on the phonological level of language systems of the Albanian and the Romanian languages. These two languages can be considered the nuclear of the Balkan language union and have most fool repertoire of balkanisms. Detailed analysis using data of historical phonology of the most representative phonetic balkanism – central vowel // leads to the conclusion that it is the result of similar phonetic processes in languages under consideration. The Balkan peculiarity of this vowel is proved by its phonematisation, i. e. involvement of this unstressed vowel [] in such specific Balkan system of oppositions as article/nonarticle opposition of forms of singular nouns of feminine forms ([]- [a] rom. cupă – cupa, alb. kupё – kupa – ‘cup’).