Helping to explain the indifference of labor unions by IO psychology is a failure to appreciate power differences of management and workers, the early attitudes toward unions of IO psychologists, and limited financial rewards. Comparing to the history of economics and sociology is the United States history of IO psychology in investigation of this hypothetical viability. The conclusion is for the neglect of labor union issues by applied psychologists are for two crucial reasons to exist being the dark of early pro-union psychologists and the reluctance of IO psychologists to address the presence of conflict between employees and employers. The major issue being addressed is the evolution of IO psychology within the United States and its ignorance of labor unions and partnership with management. In defining IO psychology, this question is important pertaining to the aim of the field. The definition of IO psychology according to the Society for Industrial-Organizational Psychology (SIOP) is the promotion of human welfare through applying psychology to the different types of organizations. For IO psychology to remain true to the mission, psychologists in working with these different organizational types include both labor and management within their endeavors. Critics and psychologists alike have documented the indifference toward organized labor of IO psychologists. This indifference involves attempts to dismantle unions already in existence and opposing unionization before it should ever begin. Numerous complaints exist of this indifference to labor unions, yet few attempts have been made in the analysis of this persistence. In investigating this indifference a review of the history of IO psychology will occur in relation to United States labor unions evaluating the ability of previous offered explanations to maintain their validity. A comparison of the history of IO psychology is often made toward other social scientific disciplines in economics and sociology. The result of this comparison is a broader context analysis occurring in the isolated examination of psychology. The focus will be on the relationship of labor unions with the practice of individual psychologists. In examining this relationship, the writings of critics and individual IO psychologists act as the sources of information along with the writings by members of organized labor and analysis of journal publication records. In comparison to other countries, IO psychology has less evolved in progression toward relations to organized labor.