In this study, it is aimed to develop a scale to determine the nomophobia levels of adolescents. The study included 884 adolescents aged 10-18. The theoretical basis was created by first reviewing the literature to reveal the structure of nomophobia in adolescents, which is the feature to be measured in the study. Similar scales were taken as a basis in the creation of the scale items. An item pool was created in line with the data obtained, and the process of determining the measurement form was carried out simultaneously with the creation of the item pool. Expert opinions were consulted for content validity in line with the validity study after the items of the scale were created. The content validity rate was calculated one by one for the items to be submitted for expert opinion. A pilot study was conducted with a psychologist and 10 adolescents attending secondary school to evaluate the appropriateness of the items and with this application, it was decided that the items were comprehensible. After the application, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted to determine the construct validity of the measurement tool, and Cronbach's alpha reliability coefficients were also calculated to determine its reliability. As a result of the study, it was found that the Nomophobia Scale for Adolescents (one-dimensional and 29 items) is a valid and reliable measurement tool for measuring nomophobia in adolescents. The results proved that the scale has the potential to measure nomophobia precisely and can be used in academic studies.