The success of mergers and acquisitions(M&A) have been evaluated by either measuring ex ante expectations for the specified time period(Window) or assessing long term-based post operating performance (ex post operating performance). In this study, utilizing cumulative abnormal return(CAR) method, M&As which are observed in both domestic and U.S. construction industries were analyzed then research outcomes are compared. Analysis results indicate that stockholders of public construction companies did not realize significant economic gains from M&As. In other words, there was no synergistic gains from the construction M&As. Also, no significant performance difference was observed between related and unrelated diversifications.