This study investigated the critical success factors that affect the effectiveness and efficiency of mergers and acquisitions, by soliciting responses from bank Chief Executives and case evidence from the South African banking industry for the period 1990 to 2015. The study applied a mixed-use methodology. The case study evidence was drawn from the formation of the “Big Four Banks” in South Africa, namely, Absa (“Barclays Africa Group”), First Rand Group, Nedbank Group and Standard Bank Group. The study found that when visions and values of merging banks were aligned, there was a greater chance of success. The study further found that culture compatibility of merging entities is paramount. Stakeholder acceptance was also found to have a strong impact on the chance of success or failure in mergers and acquisitions (M&A). The case evidence corroborated and substantiated that there was a positive Deal Value Added (DVA) trend before the merger activity and immediately thereafter, evidenced by positive share price appreciation resulting in increased market capitalisation. The quantitative results found that 56% of the sampled CEOs indicated that an 80% majority of bank mergers in the South African banking sector had created value over the long term, evidenced by 10-year return trends. This study contributes to the corpus of knowledge by generating an integrated assessment framework that can be applied even beyond the South African environment, by practitioners involved in mergers and acquisition activities. / Graduate SBL / D.B.L.