Neuropsychology is a branch of applied psychology that specializes in the assessment of brain/behaviour relationships and with the diagnosis and rehabilitation of functional problems arising from brain injury, developmental delays or other disruptions of the brain. The neuropsychological assessment provides a detailed evaluation of the client's sensory, motor and cognitive functions through tests that have been scientifically demonstrated to be sensitive to the effects of brain damage or dysfunction, using an extensive battery of tests typically including measures of sensory skills (hearing, vision and sense of touch), motor functions (strength, speed and coordination), attention/concentration abilities, memory functioning (verbal and visual-spatial), speech and language abilities, abstract thinking, intelligence and emotional/behavioural adjustment.

In neuropsychological assessment it is important to use a wide array of evaluation procedures and consider information from multiple sources to obtain a comprehensive view of the individual's neurological and psychological functioning, their response to the problem(s) and to formulate appropriate interventions and recommendations. This need to integrate a large volume of information and test data and to use it to formulate professional opinions regarding the status and functioning of the brain requires advanced training beyond the standard course work for general psychology or counselling programmes, and at a minimum the neuropsychologist will have completed additional advanced studies in neuroanatomy and neuropathology, clinical psychopathology and specialized neuropsychological testing procedures.

A major objective of neuropsychological assessment is to provide a detailed description of the wide range of the psychological abilities that are most essential for adaptive functioning in real life situations (such as school, work and social settings).

Such adaptive abilities are often seriously disrupted by physical damage to the brain, but they may also be significantly impaired even in less severe forms of neurological dysfunction without physical evidence of structural brain damage. This type of assessment is often of great assistance in the diagnosis and treatment planning for many conditions such as Attention Deficit Hyperactivity Disorder, Learning Disabilities or Developmental Disorders (including generalized cognitive delays as well as pervasive developmental disorders such as Autism and Asperger's Syndrome), in addition to conditions with known brain injury or maldevelopment from trauma or prenatal exposure to drugs and/or alcohol.

Neuropsychological assessment provides the most accurate and valid means of determining the extent of cognitive impairment resulting from such brain damage or dysfunction and to measure changes in such functioning when it is suspected that there may be either recovery or deterioration over time. Neuropsychological assessment has also become an important component in the evaluation of disability status in many personal injury and disability insurance claims, particularly when the nature of the injury or illness may give rise to significant handicaps in motor, sensory or cognitive processes, or when a detailed evaluation of the individual's current functioning is critical to determine residual employability for rehabilitation or retraining purposes. Neuropsychological assessment is also often a critical component of the evaluation process for legal competence issues such fitness to stand trial, criminal responsibility and capacity for consenting to treatment, signing legal documents or writing/modifying a last will and testament.