PurposeOrthorexic tendencies are increasingly prevalent among children and adolescents. This study set out to investigate the reliability and validity of the Turkish version of the Orthorexia Nervosa Inventory (ONI) in a clinical adolescent sample.Methods266 adolescents aged 12–18 years, who applied to the Department of Child and Adolescents Psychiatry were included in the study. Participants completed sociodemographic data form, ONI, Eating Attitude Test, Revised Child Anxiety and Depression Scale-Child Version and ORTO-15.ResultsThe Cronbach’s alpha coefficient for the ONI reached 0.92, indicating very good internal consistency. Total factor scores and Cronbach alpha values for behaviors, impairments, and emotions were found to be 0.84, 0.84, and 0.83, respectively. The CFA performed supported the three-factor structure of the ONI obtained in the first sample. The minimum discrepancy per degree of freedom = 1.89 and the model generally fit well to the structure (RMSEA = 0.058, SRMR = 0.033, CFI = 0.92, TLI = 0.91).DiscussionThis study has shown that the Turkish version of the ONI is a valid and reliable scale for specifying the tendency for Orthorexia Nervosa in a Turkish adolescent population. These findings contribute in several ways to our understanding of orthorexic tendencies and provide a basis for more concrete research data that can be obtained by using the ONI, which is a reliable scale in studies to be conducted among adolescents.Level of evidenceLevel V, descriptive cross-sectional study.