The purpose of this paper is to examine the impact of mergers and acquisitions on employee performance in Greek banking sector over the period 1996-2004. By measuring four financial ratios, we find controversial results about the performance of employees following merging activity in Greek banking industry. Results are expected, since mergers and acquisitions represent a disorienting dilemma for employees which can have both positive and negative impact on their performance. Disorienting dilemmas lead to stress and anxiety because employees are confronted with an experience such as a merger and an acquisition that leads them to review their views, thereby altering their perspectives. Such a dilemma may serve as an impetus for transformative learning. Transformative learning assists employees in merged banks to acquire productive thinking styles and practices. The paper presents an explanation why merging activity in the Greek banking system has ambiguous effects on employee performance and suggests the implementation of Transformative Learning.