Organizational socialization is the process by which people learn about, adjust to, and change the knowledge, skills, attitudes, expectations, and behaviors needed for a new or changing organizational role. Thus, organizational socialization focuses on organizational membership, which includes how people move from being outsiders to being insiders and how people move between organizational roles within and across organizations over time. To date, research has focused on how employment organizations encourage newcomers to align with existing role expectations via tactics that encourage assimilation. However, organizational socialization is a dynamic process of mutual influence. Individuals can also influence and shape the organization to align with their desires, via personalization tactics. Thus, organizational socialization describes the process by which an individual assumes a new or changing role in ways that meet organizational and individual needs. Most research on organizational socialization focuses on how newcomers enter paid work environments. Researchers often focus on the tactics organizations use to encourage people to assimilate into the organization during the early or entry stage. Less attention has been given to the later stages of organizational socialization (active participation, maintenance, exit, and disengagement), non-work organizations, and transitions between roles within an organization. However, a growing body of research is considering organizational socialization into volunteer roles, new or changing roles, and later stages of socialization such as exit and disengagement. Scholars and practitioners also increasingly recognize how individual, organizational, contextual, and technological factors (e.g., socioeconomic status, race, gender, new information and communication technologies, time, and boundaries) may alter how organizational socialization works and with what effects—thereby offering insight into the underlying processes implicated in organizational socialization. Future areas of research related to context, time, boundaries, communication, and the ethics of organizational socialization are highlighted.