Applied psychology is the use of psychological methods and findings of scientific psychology to solve practical problems of human and animal behavior and experience. Educational and organizational psychology, business management, law, health, product design, ergonomics, behavioural psychology, psychology of motivation, psychoanalysis, neuropsychology, psychiatry and mental health are just a few of the areas that have been influenced by the application of psychological principles and scientific findings. Some of the areas of applied psychology include counseling psychology, industrial and organizational psychology, engineering psychology, occupational health psychology, legal psychology, school psychology, sports psychology, community psychology, neuropsychology, medical psychology and clinical psychology, evolutionary psychology, human factors, forensic psychology and traffic psychology. In addition, a number of specialized areas in the general area of psychology have applied branches. However, the lines between sub-branch specializations and major applied psychology categories are often mixed or in some cases blurred. For example, a human factors psychologist might use a cognitive psychology theory. This could be described as human factor psychology or as applied cognitive psychology. When applied psychology is used in the treatment of behavioral disorders there are many experimental approaches to try and treat an individual. This type of psychology can be found in many of the subbranches in other fields of psychology.

Forensic psychology is the practice of psychology applied to the law. Forensic psychology is the application of scientific knowledge and methods to help answer legal questions arising in criminal, civil, contractual, or other judicial proceedings. Forensic psychology includes research on various psychology-law topics, such as jury selection, reducing systemic racism in criminal law, eyewitness testimony, evaluating competency to stand trial, or assessing military veterans for service-connected disability compensation. The American Psychological Association's Specialty Guidelines for Forensic Psychologists reference several psychology subdisciplines, such as social, clinical, experimental, counseling, and neuropsychology.