This study was conducted to examine the impact of the operating synergy, financial synergy and firm reputation toward firm performance in merger and acquisition processes. This study also examines how firm reputation moderates the impact of operating synergy and financial synergy toward firm performance. The object of this research are companies involved in mergers and acquisitions between 2010 and 2016. Design/methodology/approach: The purposive sampling method is used to select the research sample. The descriptive statistical test, outlier test and hypothesis test is used to analyze the data using e-eviews program. The study assumed Buy and Hold Abnormal Return (BHAR) as the performance to measure a successful acquisition, and the factors that have an impact on acquisition performance are taken as being operating synergy, financial synergy and firm reputation. Findings: The results of this study show that by maximizing the operating synergy and firm reputation, this can improve the BHAR of an acquisition event, and a firm will a weak reputation can strengthen the BHAR by maximizing the operating synergy. Practical implications: These findings will be very helpful to management to maximize their firm performance using merger and acquisition as their strategy and firm reputation as their intangible resources. Originality/value: This article provides a new insight of acquisition research as to how firm reputation moderates the impact of acquisition synergy to achieve firm performance.