应用心理学的基本前提是运用心理学的原则及理论来克服其他领域中实际的问题，例如管理学、产品设计、人因工程学、营养学、法律及临床药物. 应用心理学不但包含以下领域:工业与组织心理学、法庭心理学, 人因工程学，也包含了教育心理学、运动心理学及社区意识。另外，一些心理学的专门领域也有应用心理学的分支(例如:应用社会心理学，应用认知心理学)。

应用心理学的奠基者，雨果·明斯特堡。和1800年代晚期许多胸怀大志的心理学家一样，这位德国学者前往美国，起初是为了学习哲学。明斯特堡对心理学的领域有多方兴趣，例如: 目的心理学、社会心理学以及法庭心理学。1907年，他撰写了有关证词的法律观点、自白以及法庭进程的一些杂志文章，最后集结成书 - On the Witness Stand。接下来几年，应用心理学派进入了哈佛心理实验室。九年内，他以英文撰写了八本书，将心理学应用于教育、工业效率、管理以及教学。雨果·明斯特堡的贡献使他成为应用心理学的创始者和奠基人。

Applied psychology is the use of psychological methods and findings of scientific psychology to solve practical problems of human and animal behavior and experience. Mental health, organizational psychology, business management, education, health, product design, ergonomics, and law are just a few of the areas that have been influenced by the application of psychological principles and findings. Some of the areas of applied psychology include clinical psychology, counseling psychology, evolutionary psychology, industrial and organizational psychology, legal psychology, neuropsychology, occupational health psychology, human factors, forensic psychology, engineering psychology, school psychology, sports psychology, traffic psychology, community psychology, medical psychology. In addition, a number of specialized areas in the general field of psychology have applied branches (e.g., applied social psychology, applied cognitive psychology). However, the lines between sub-branch specializations and major applied psychology categories are often 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.