The relationship between assistive technology for cognition (ATC) and cognitive function was examined using a systematic review. A literature search identified 89 publications reporting 91 studies of an ATC intervention in a clinical population. The WHO International Classification of Functioning, Disability and Health (ICF) was used to categorize the cognitive domains being assisted and the tasks being performed. Results show that ATC have been used to effectively support cognitive functions relating to attention, calculation, emotion, experience of self, higher level cognitive functions (planning and time management) and memory. The review makes three contributions: (1) It reviews existing ATC in terms of cognitive function, thus providing a framework for ATC prescription on the basis of a profile of cognitive deficits, (2) it introduces a new classification of ATC based on cognitive function, and (3) it identifies areas for future ATC research and development.