Psychological assessment is similar to psychological testing but usually involves a more comprehensive assessment of the individual. Psychological assessment is a process that involves  the integration of information from multiple sources, such as personality tests, tests of cognitive ability or intelligence, interest tests, or aptitude tests, as well as information from personal interviews. Collateral information is also collected about personal, occupational, or medical history,  from interviews with parents, spouses, or teachers.

A psychological test is one of the sources of data used within the process of assessment and usually more than one test is used.

Many psychologists do some level of assessment when providing services to clients or patients, to assess a particular area of functioning or disability often for school settings; to help select type of treatment or accommodation; or to help assess job seekers and provide career development counseling.

Psychological testing is a field characterized by the use of samples of behavior in order to assess psychological construct(s), such as cognitive and emotional functioning, about a given individual. The technical term for the science behind psychological testing is psychometrics. By samples of behavior, one makes observations of an individual performing tasks that have usually been prescribed beforehand. These responses are often compiled into statistical tables that allow the evaluator to compare the behavior of the individual being tested to the responses of a norm group.

The psychological assessment process for adults usually involves about eight hours of testing. For children it generally takes four to six hours. The results are then examined and interpreted to the clients.