Objective: The attachment style may be decisive for the substance use proclivity. The aim of this study was to determine the proclivity of substance use among medical students and to investigate the relationship between attachment style and substance use proclivity. Methods: Volunteer students studying at Eskisehir Osmangazi University Faculty of Medicine between April 2019 and June 2019 were enrolled in the study with snow ball method. In our study, Sociodemographic Information Form, Substance Abuse Proclivity Scale (SAP) and Experiences in Close Relationships-Revised Scale (ECR-R) were used as data collection tool. 214 students who accepted to participate to the study were evaluated. Results: Seventy three (34.1%) students had tendency to substance use evaluated by the SAP. While there was no statistically significant difference between the ECR-R total (143.78±15.79 and 139.57±17.91) and ECR-R avoidance subscale (75.98±10.40 and 77.14±8.64) mean scores of students with and without substance use proclivity (z=-1.543, p=0.123; z=0.70, p=0.487, respectively), the mean score of the ECR-R Anxiety subscale (68.06±12.75 and 63.50±14.13) was higher in students with substance use proclivity (z=-2.45, p [Anadolu Psikiyatri Derg 2020; 21(4.000): 367-372]