Learning is a complicated process, notwithstanding the fact that the individual learners, particularly adults, are complicated beings. Adult learning is a subject of ever-growing interest. With the changing demographic situation of the developed world, there has been a focus on the concept of lifelong learning. Studying adult learning theory is rapidly growing across the globe in the context of human resource development. The application of equity theory and its impacts are rarely considered in studies of adult learning and human resource development, and the link between the two theories are remains unclear. In fact, the role of equity theory and its impacts are rarely considered in studies of adult learning and human resource development. Hence, through the structured literature review, this chapter explores the role of equity theory in the context of adult learning theory and through that identifies the theoretical gaps and gives suggestions for future research.