© 2020 IJLS; Printed in the USA by Lulu Press Inc.In EFL context, where English is the medium of instruction at select universities, university students aim to develop foreign language writing skills for academic and professional purposes. However, higher language proficiency in itself cannot guarantee success in writing. Self-efficacy, the individual judgement of their capabilities, seems to play an important role in individuals’ writing performance and the effort given to writing tasks. The objective of this study is to measure Turkish university students’ foreign language writing self-efficacy and to identify the variables that may be related to foreign language writing self-efficacy. A newly developed and validated foreign language writing self-efficacy scale was implemented to collect data from students taking a writing class at a private university. Results indicated that the participants’ foreign language writing self-efficacy is moderate, and that their writing self-efficacy does not change due to their gender, or actual English language proficiency levels. Perceived language proficiency seems to play a more prominent role than actual proficiency level.