2.1 INTRODUCTION The first chapter of this thesis identified organizational commitment (OC) as the way to improve a wide range of positive organizational outcomes and to cure turnover and absenteeism. It is essential to have a thorough understanding of the general concept of OC. Therefore, the main objective of this chapter is to provide a review of OC based on an extensive search of the existing literature. This chapter begins with the theoretical background of OC and its definition in the current world. Different OC approaches will then be discussed and the three-component model will be presented in detail. In this chapter we proceed with the evaluation of OC in the construction sector based on the existing literature. Finally, a summary is provided at the end of this chapter. 2.2 BACKGROUND AND DEFINITION OF ORGANIZATIONAL COMMITMENT (OC) Commitment is a multi-focused concept. One can find commitment to professional associations, unions, work groups as well as commitment to family, state or religion, projects, values ​​or career (Reichers, 1985; Baruch, 1998; Meyer & Herscovitch, 2001; Paillé , Fournier and Lamontagne 2011). OC is one of the five forms of work commitment indicated by Morrow (1983) and has been conceptualized in different constructs, definitions and interpretations to better understand the intensity and stability of an employee's dedication to the organization (Cohen, 2007; Singh & Venugopal, 2008). The first attempt to conceptualize commitment is that of Becker's (1960) side gamble theory. He argued that an individual is committed to an organization because of hidden investments. The threat of losing these investments, coupled with the perceived lack of alternatives to replace or offset the paper half, is essential in undertaking project activities to achieve objectives. For the QS, achieving goals within the work group creates a positive influence for being a member of the group. Therefore, QS is likely to gain or maintain its group membership (Chiu & Ng, 2013). To achieve the desired attitude and behavioral changes among employees, it is essential to understand the goals, expectations, and goals of the organization and the employees (Mohyin, Dainty, & Carrillo, 2009). Failure to understand what employees require and expect from the employment relationship often leads to deterioration of commitment and loyalty and therefore increased employee turnover (Loosemore et al., 2003). This reflects the need to study the antecedents of OC among QSs, through looking at QSs working in different consultancy and construction companies to fill gaps in knowledge.