Attention deficit hyperactivity disorder (ADHD) is seen frequently in childhood and leads to marked impairment in functioning. There is no scale in Turkey with documented validity and reliability that assesses ADHD-specific functional impairment (FI). This study aimed at adapting the Weiss Functional Impairment Rating Scale-Parent Report (WFIRS-P), which assesses ADHD-related FI, for use in Turkey, and examining psychometric aspects of the scale. The study included 250 children diagnosed with ADHD and 250 healthy children and their parents. Internal consistency and test-retest methods were used to test the reliability of the scale. Validity was tested with exploratory and confirmatory factor analyses and convergent and discriminant validity analyses. Since all six questions of the WFIRS-P were scored 0, analyses were conducted for the original scale questionnaire consisting of 50 items and the questionnaire consisting of 44 items where the six questions scored 0 were not included. The Cronbach's alpha coefficient was 0.93 for the whole scale. The Spearman's correlation coefficient was 0.93 for test-retest reliability. The exploratory factor analysis run on the 44-item questionnaire showed that the scale items were best represented in a 7-factor structure, but some items were placed in different subdomains than those of the original scale. In the confirmatory factor analysis, the root mean square error of approximation was 0.061, and the comparative fit index was 0.95 for the whole model. Therefore, the Turkish WFIRS-P is valid and reliable in testing functional impairment in children with ADHD.