The aim of the study was to describe the validity and reliability of the Turkish version of Juvenile Arthritis Functional Assessment Report (JAFAR) in children/adolescents with Juvenile Idiopathic Arthritis (JIA). Sixty-nine children/adolescents with JIA were included in the study. JAFAR(TR)-Child and Parent forms were applied to the patients with JIA and to their parents for test retest at one-week intervals, the patients did not receive additional treatment and his/her pharmacological treatment did not change for that week. Test-retest reliability was evaluated by intraclass correlation coefficient (ICC), and internal consistency reliability of multi-item subscales was evaluated by calculating Cronbach's alpha coefficient. Correlations between JAFAR(TR)-Child and Parent with the Pediatric Quality of Life Inventory 3.0. Module Arthritis (PedsQL), the Childhood Health Assessment Questionnaire (CHAQ), and the Juvenile Arthritis Disease Activity Score (JADAS) were evaluated to determine construct validity. The ICC value for the test/retest reliability of JAFAR(TR)-Child was 0.963 and of JAFAR(TR)-Parent was 0.576. JAFAR(TR)-Child total score had low to moderate correlations with PedsQL Child (r=-0.34; p=0.004), CHAQ (r=0.40; p=0.001), and JADAS total score (r=0.42; p=0.000). JAFAR(TR)-Parent total score had moderate to high correlations with PedsQL Parent (r=-0.55; p=0.000), CHAQ (r=0.72; p=0.000) and JADAS total score (r=0.53; p=0.000). The Turkish version of JAFAR was found to be clinically valid and reliable in JIA.