The aim of the current methodological study was to develop a psychometric measurement tool for determining internet gaming disorder (IGD) based on family members' responses. The sample comprised 173 adolescents and their families. For reliability, the scale was created using item-total correlation, internal consistency coefficient, and test-retest correlation methods. The validity of the scale was evaluated using content validity index (CVI), construct validity, explanatory factor analysis (EFA), and confirmatory factor analysis (CFA). CVI for the scale was 0.92, Cronbach's alpha coefficient was 0.963, and item-total correlation ranged between 0.67 and 0.81. In the EFA, 61.7% of the total variance on the one-dimensional scale was explained and item factor loads ranged between 0.71 and 0.84. CFA showed good fit of the model. Thus, the Gaming Disorder Scale-Family Form, which was proven to be a valid and reliable measurement tool, is recommended for use by health care providers and community partners in the evaluation of potential IGD in adolescents. [Journal of Psychosocial Nursing and Mental Health Services, 59(11), 25-32.].