Due to popularization of internet and e-commerce, more and more people getting involved in online shopping market. A large number of companies have been transferred to the internet where online customers have been increased due to easy access. The online business facilitates people to communicate without knowing each other. The e-commerce systems are the combination of commerce behavior and internet technologies. Therefore, trust aspects are positive elements in buyer-seller transactions and a potential source of competitive e-commerce industry. There are two different approaches to handle the trust. The first approach has a solid authentication set of rules where decisions are made on some digital or logical rules called policy based trust mechanism. The second approach is a decentralized trust approach where reputation assembled and shared in distributed environment called reputation based trust mechanism. Objectives: In this thesis, the strengths and weaknesses of policy and reputation based trust mechanisms have been identified through systematic literature review and industrial interviews. Furthermore, the process of integrated trust mechanism has been proposed. The integrated trust mechanism is proposed through mapping process, weakness of one mechanism with the strength of other. The proposed integrated trust mechanism was validated by conducting experiment with buyer/seller scenario in auction system. The analysis of collected results indicated that proposed integrated trust mechanism improved the trust of buyer against eBay and Tradera. At the end, we have discussed some key points that may affect trust relationship between seller and buyer. Furthermore, there is a need for further validation of proposed trust mechanism in auction system/e-commerce industry.