This research was conducted to see the influence of board characteristics, the firm size on firm value, and financial performance on companies with completed mergers and acquisitions on the Indonesian stock exchange. This study was used to look at financial performance, specifically in 7 years after the company made a merger from 2013-2020. This research instrument uses quantitative analysis data by testing predetermined hypotheses. The study also found that not all variables significantly impact the company's firm value and financial performance when conducting mergers. The main finding is that the more excellent board characteristic of the merger company will result in no improvement in the company's financial performance; this is due to a large number of improper decision-making actions because the rules issued by the board hinders it.