Objective: In an effort to reduce disparities in ADHD diagnoses and treatment across cultures, the current study sought to establish initial psychometric and cultural properties of the ADHD-FX: a culturally sensitive assessment measure of functional impairment related to ADHD for diverse families. Method: Fifty-four Latino parents (44 mothers and 10 fathers) of school-aged children completed the ADHD-FX, as well as several other measures assessing child behavior and parent acculturation. Results: The ADHD-FX demonstrated adequate reliability (as demonstrated by internal consistency and test–retest reliability), psychometric construct validity (as demonstrated by associations with theoretically related measures), and cultural validity (as demonstrated by or lack of associations with acculturation measures). Conclusion: Initial psychometric and cultural properties suggest that the ADHD-FX is a reliable, valid, and culturally appropriate measure to assess functional impairment related to ADHD (i.e., difficulties with academic achievement, social competence, and familial relationships) in an at-risk, school-aged population.