A large majority of university students use social networking sites (SNSs) actively. Nevertheless, there are very limited studies examining students' perceptions about student-teacher relationships in SNSs comprehensively. The purpose of this research was to investigate university students' perceptions about interacting with their teachers in SNSs, and to this end an exploratory mixed-methods design was utilised. Qualitative data were collected from 21 students via interviews, and quantitative data from 1,324 students in 19 universities in Turkey via a questionnaire. Content analysis, descriptive analysis and principal component analysis methods were used to analyse the data. The content analysis contributed to the formulation of the questionnaire items. The principal component analysis yielded the following four dimensions: perceived utility, perceived barriers, perceived favourable teacher behaviours, and perceived unfavourable teacher behaviours. The most prominent finding is that the students were mostly opposed to their teachers' sharing their political and religious views; however, they were in favour of teachers sharing information about their personal life. Despite some students displaying some hesitation, especially concerning the level of respect between them, the majority of students had a positive outlook towards teacherstudent friendships. The students indicated that being friends on SNSs would increase their motivation towards the course.