In this study, we investigate a change in acquirers' information asymmetry during mergers and the effects of changes in acquirers' and their suppliers' and customers' information asymmetry on their bondholders' wealth by using American market data from 2001 to 2006. We find that acquirers' information asymmetry declines significantly before merger announcement dates, which benefits acquirers' bondholders (i.e., the information premium effect). Additionally, we find that the relative information advantage effect is more essential in the post-announcement period (i.e., increases in suppliers' and customers' information asymmetry negatively affect acquirers' bondholders' wealth).