A challenge for foreign language learners is the correspondence of the written language with the sounds of the target language. Although the sound-to-letter relationship of German is not as complicated as English or French, the German language does not have total sound-to-letter correspondence. The aim of this study is to question which sounds are more problematic for multilingual Turkish German learners in university education. A further aim is to determine the possible causes of their pronunciation deviations. In the context of the present study, an error analysis in the sense of Kleppin (1998) was carried out. The sample of the study was a group of Turkish university students who learned German as a third foreign language. To collect the data, the respondents were asked to perform a number of actions: to pronounce a list of selected words, record themselves with electronic recording devices and then send the digitally stored recorded files to the researchers. The deviations were dominated by vowels, including diphthongs and vowels with umlauts, which was expected. The causes of the deviations were mostly due to the interferences of the written language and the previously learned (foreign) languages. From the results, it can be concluded that multilingual learners have many advantages in pronunciation skills and that the deviations are due to the interference of the written language and the previously learned (foreign) languages rather than errors.