The aim of the present study was to examine the measurement invariance (MI) of the reading, mathematics, and science tests in terms of the commonly used languages. It also aimed to examine the differential item functioning (DIF) of the PISA test, the original items of which are in the languages of English and French, in terms of the language variable. As a result of the MI analyses, it was concluded that the best working model for the reading comprehension, mathematics and science tests in terms of the commonly used languages for all three tests was the strong factorial invariance model. As a result, it was found that MI could not be established for any of these tests. Moreover, the analyses indicated that population heterogeneity (PH) could not be obtained in any of the three tests, and that the latent means for these tests were not equal. Furthermore, DIF was identified in more than half of the items. It can be deduced that this condition may result in an increase in the number of items with DIF specifically in terms of the variety in the number of languages.