Although there are many instruments for assessing activities of daily living (IADL) in brain injured patients, few instruments specifically target cognitive impairment and its impact on IADL. The present study presents the development of the Profinteg instrument, a tool for real-life assessment as well as rehabilitation of IADL in patients with cognitive impairment. This two-stage instrument covers over 90 activities. Psychometric properties of the different Profinteg measures were explored in twenty-five patients with mild to severe cognitive difficulties and twenty-five caregivers. The feasibility of the Profinteg rehabilitation procedure was explored in three patients. Excellent interrater reliability (r > 0.90,p < 0.01) was observed for all measures. Good sensitivity to changes in IADL disability over time was also observed (T= 2.37,p < 0.02). Significant improvement of IADL functioning was found after rehabilitation guided by Profinteg assessment. The Profinteg instrument detects with precision the difficulties patients encounter in their real-life setting via (I) assessment of a large number of activities and (2) detailed decomposition of activities into sub-activities. The Profinteg tool also provides promising results for guidance of IADL rehabilitation in the patient's real-life environment.