This paper examines the impact of mergers on the financial performance of the Jordanian banking sector. This paper applies the financial approaches in analysing the effects of mergers on Jordanian banks’ performance for two the periods: four years pre-merger and four years’ post-merger for the period from 2001 to 2009. The sample of the study solely contains the case of the merger of the Jordan Ahli Bank (AHLI bank) with Philadelphia Bank in 2005. Data are tested for normality using the Shapiro-Wilk Test and Kolmogorov Smirnov test. The financial ratios and a statistical technique as a Mann-Whitney U test were used to assess the significant differences in the financial performance of the selected banks pre- and post-merger by investigating the performance-related financial ratio groups that are expressed by leverage, liquidity, efficiency, and cash flow ratio. The results show that there is an insignificant improvement in the ratios of AHLI bank in the period after the merger, except for the superior result provided by this study indicating that the leverage ratios improved significantly. The reason for the insignificant improvement in financial ratios may be that the post-merger period corresponds to the period of the global financial crisis that began in 2007.