Organizational commitment is a well-established work-related psychological construct that has long been considered one of the core barometers of the individual_organization relationship. More recently, the concept of employee engagement has emerged as an important stand-alone construct that also helps to define and index the individual_organization relationship. Whilst there has been a lack of consensus regarding the definition and measurement of both commitment and engagement, the degree to which the two constructs are distinct has also been the subject of ongoing debate. This chapter describes research evidence regarding the nature, direction, and strength of the relationship between employee engagement and organizational commitment. The chapter also provides an overview of the theoretical platforms underpinning each construct, the evidence regarding the antecedents and outcomes associated with each construct and its dimensions, the stability of each construct over time, and the nature and efficacy of different interventions that have been applied to develop each construct. Finally, an agenda for future research is offered.