Purpose - This study aims to examine the long-term impact of mergers and acquisitions (M&As) on firm performance, particularly within the pharmaceutical industry. Using a panel data regression model, the study assesses how key financial ratios such as Net Profit Margin, Return on Capital Employed (ROCE), Debt to Equity Ratio, and Enterprise Value influence postmerger firm performance over time. Design/methodology/approach - A panel data approach has been conducted using data from 10 pharmaceutical companies from their post-merger period, focusing on the effects of M&As on firm performance as measured by Net Profit Margin. Financial ratios related to profitability, liquidity, and valuation were used as independent variables. Findings - The study finds that M&As have a positive long-term impact on firm performance, particularly in companies with strong Earnings per Share (EPS), efficient capital management, and good liquidity. ROCE, Debt to Equity Ratio, and Current Ratio were significant predictors of improved Net Profit Margin, highlighting the importance of financial efficiency and debt management in the post-merger phase. Research limitations/implications - The focus on the pharmaceutical industry limits the generalizability of the findings to other sectors. Future studies should examine a broader range of industries to better understand the effects of M&As across different contexts