The role and impact of behavioural factors in the business customers&amp;rsquo; decision to outsource a service to a third party logistics (3PL) provider is the subject of this thesis. Unless it is understand what extent the decision to use 3PL is driven by behavioural factors, it will hardly know how best to improve the quality of 3PL decision making process that can promote strong growth in logistics based industries and be compatible with global customer demands. Applying the theory of planned behaviour as the theoretical foundation for modeling business customers&amp;rsquo; intention, it investigates how attitude, subjective norm and perceived behavioural control predict the intention to use 3PL, and whether such intention is translated into the actual 3PL use or not. The behavioural model is built in the context of Bangladesh; 243 business organisations are at its core. The structural equation modelling results show that, business customers who exhibit a positive attitude tend to favour 3PL use. The perceptions of social pressure, exerted from operating in a competitive environment, and of the capacity and control to make decisions, are indicative of a positive decision to outsource services to 3PL providers. The multi-group invariance test shows that, there is no difference in intention between 3PL users and non-users. To promote greater use of outsourcing services in a developing country like Bangladesh, it is important to streamline existing 3PL decision making processes so that the resulting improved 3PL environment can play a key role in its efforts to maintain strong growth in logistics based industries that are compatible with global outsourcing practices