Objective: The aim of this study was to determine the effect of social phobia and peer pressure on substance use among adolescent. Methods: The study was conducted in three high schools in the city of Van/Turkey between November 2015-July 2017. The descriptive study was conducted with 1996 adolescents using face-to-face data collection method. Data were collected using a sociodemographic questionnaire, Social Phobia Scale for Children and Adolescents (SPSCA), and Peer Pressure Scale (PPS). The data were collected face to face in the classroom environment. All ethical principles were observed in the study. Results: It was determined that the SPSCA and PPS mean scores of adolescents were at a low level. The mean PPS and SPSCA scores of adolescent were found to be positively and weakly correlated (p < .05). It was concluded that there was a statistically significant difference between the mean SPSCA and PPS scores of adolescent who smoke tobacco and drink alcohol (p < .001). Conclusion: As the result of the research, it is identified that substance use among adolescents is at a considerable level. It is observed that several sociodemographic variables are effective in substance use on peer pressure and social phobia perceived by adolescents. It is recommended that school health nurses include the topic “the effect of social phobia and peer pressure on substance use” in training programs.