real world procurement transactions often involve multiple attributes and multiple vendors. successful procurement involves vendor selection through appropriate market mechanisms. the advancement of information technologies has enabled different mechanisms to be applied to similar procurement situations. advantages and disadvantages of using such mechanisms remain unclear. the presented research compares two types of mechanisms: multi-attribute reverse auctions and multi-attribute multi-bilateral negotiations in e-procurement. both laboratory and online experiments were carried out to examine their effects on the process, outcomes and suppliers’ assessment. the results show that in procurement, reverse auctions were more efficient than negotiations in terms of the process. auctions also led to greater gains for the buyers than negotiations but the suppliers’ profit was lower in auctions. the buyer and the winning supplier jointly reached more efficient and balanced contracts in negotiations than in auctions. the results also show that the suppliers’ assessment was affected by their outcomes: the winning suppliers had a more positive assessment towards the process, outcomes and the system. the findings are consistent in both the laboratory and online settings. the implications of this study for practitioners and researchers are discussed.