Introduction Driving is a complex activity involving a high level of cognitive abilities and thus might be affected after a brain injury/disease. The aim of this research was to evaluate the feasibility and construct validity of a driving simulator tool as a complement to existing driving assessments of patients with cognitive dysfunctions after a brain injury/disease. Method A descriptive and prospective research design was achieved. For construct validation, decisions were based on results from the Useful Field of View, Nordic Stroke Driver Screening Assessment, Trail Making Test and, when necessary for the decision, an on-road observation. Results from the simulator tool were not included in the clinical decision process. Results A total of 129 patients from four different rehabilitation services were included. The results showed a significant difference in test results between those who were considered medically fit versus unfit to drive. A factor analysis revealed four components, all including attention in combination with processing speed, visuospatial function, simultaneous capacity and executive function; these are all represented in the simulator tool. A correlation analysis showed that simulator subtest 3 (response/divergent response to stimuli) had the strongest correlation with most of the other tests included. Conclusions The simulator was found to be feasible and valid and found to include components other than those measured in the other tests.