There is a complex relationship between social media use and mental health outcomes. To explore this complexity and understand how social media influence adolescent mental health, a two-phase, explanatory sequential mixed-method study will be conducted. Firstly, the quantitative phase will involve surveying a healthy sample of 400 adolescents attending secondary schools in the UK (n=200) and Turkey (n=200). We will use the survey to investigate the moderating effect of relational orientation in a cross-sectional study, in which participants will be selected from secondary schools in Portsmouth, United Kingdom and Kayapinar, Diyarbakir, Turkey. Secondly, the qualitative phase will involve interviewing a mixed sample of 10-12 clinical and non-clinical adolescents in London. In these interviews, we will explore key quantitative findings in more detail, for example, how and why adolescents use social media and the role of social media in the development and maintenance of mental health well-being. The strengths and limitations of the study proposal have been discussed. Keywords: social media, anxiety, depression, adolescents, culture, relational orientation