English-medium instruction in non-English speaking countries has gained prominence around the world in the last decades due to the internationalization of higher education but the way English is used in higher education varies. To investigate this further, we focused particularly on the use of English in psychology departments across Turkish universities because psychology is one of the fields in which English is the dominant language globally. Data were collected from official reports and from 287 psychology students who evaluated the use of English in their programs by responding to a questionnaire. English was the medium of instruction in 31 out of 79 programs (about 40%) of all offered undergraduate psychology degrees in Turkey in 2015, but their measures for students' proficiency varied. Students reported that the amount of English used in their classes did not change over the course of their undergraduate psychology program. Students also stated that their comprehension level increased during their study. They also reported that some core courses should be taught or supported by materials in Turkish. The results showed that as the internationalization of higher education continues increasing, so does English-medium instruction especially in the fields such as psychology.