This article presents an investigation of language understanding within the framework of receptive multilingualism. That Turkish and Azerbaijani are closely related languages within the Oghuz branch of the Turkic languages leads to the assumption that Turkish and Azerbaijani are mutually intelligible languages. That is, speakers of these two different languages of Turkic origin can comprehend each other without much difficulty. This article aims to consider whether these languages are, in fact, as mutually intelligible as estimated, especially on the part of the Turkish speakers. In other words, within the framework of this study, the focus is on how well Turkish speakers understand written and spoken Azerbaijani. In addition, the study asks whether there is any risk of understanding failure on the part of Turkish speakers and, if yes, it will examine the grounds of such understanding failure. The results of this study in which 30 Turkish participants took part show that even though Turkish and Azerbaijani are typologically similar languages, on the part of Turkish speakers the intelligibility is not as high as is estimated.