The present research investigates how definitions of national in-group boundaries predict inter-group attitudes in Turkey. In Study 1, we explore definitions of Turkish in-group boundaries as well as perceptions of the Turkish in-group's relations with other groups among 64 university students. In Study 2, conducted among 324 university students, exploratory factor analyses reveal two dimensions of Turkish in-group boundaries: national participation (a more civic definition) and national essentialism (a more ethnic definition). They also reveal four dimensions of the relations with others. Regression analyses show that national participation predicts more negative inter-group attitudes. However, national essentialism is not found to predict the inter-group attitudes. These results are compared with those of previous studies, mostly conducted in Western countries. The comparison suggests that conclusions about the positive role of Civic and the negative role of Ethnic/Cultural definitions in intergroup relations may be less general than is previously thought.