Objective: To analyze the psychometric properties of the French version of the Weiss Functional Impairment Rating Scale–Self Report (WFIRS-S) in a large clinical sample of adults with ADHD. Method: Patients ( N = 363) were diagnosed with ADHD according to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) criteria. Psychometric properties of the French version of the WFIRS-S were tested including construct validity with a confirmatory factor analysis, internal structural validity with Cronbach’s alpha coefficient, external validity by correlations with the Beck Depression Inventory–II (BDI-II), and the EuroQol five-dimension (EQ-5D) questionnaire. Results: The confirmatory factor analysis found the following: root mean square error of approximation (RMSEA) = 0.061, 90% confidence interval (CI) = [0.058, 0.063]; comparative fit index (CFI) = 0.67. Cronbach’s alpha coefficient was .91. Correlations with EQ-5D descriptive index, visual analogue scale (VAS) scores, and BDI-II scores were –0.48, –0.55, and 0.53, respectively. Conclusion: The French version of the WFIRS-S is a psychometrically acceptable self-reported questionnaire for the multi-domain evaluation of functional impairments in adults with ADHD, for research and clinical purposes.