Post-acquisition performance evaluation is critical to understanding the long-term success and strategic value of mergers and acquisitions (M&A). This study adopts a multidimensional analytical approach to assess the impact of acquisitions across three key performance domains: financial results, customer retention, and employee efficiency. Utilizing a mixed-methods framework, the research combines quantitative financial data with qualitative insights from case studies and stakeholder interviews. Financial metrics such as revenue growth, profitability ratios, and return on investment are examined pre- and post-acquisition. Customer retention is evaluated through customer lifetime value, churn rates, and satisfaction scores, while employee efficiency is analyzed using performance benchmarks, turnover rates, and engagement levels. The findings reveal that while financial performance tends to improve in the short term, sustainable success depends heavily on strategic integration efforts that maintain customer loyalty and enhance employee productivity. The study offers practical implications for corporate managers and decision-makers, highlighting the importance of balanced post-acquisition strategies that align financial goals with human capital and customer relationship management. Recommendations for post-acquisition integration and performance tracking are proposed to support long-term organizational value.