This study explores the challenges and strategies of cultural harmonization during acquisitions in Nigeria's banking sector, focusing on the acquisition of Diamond Bank by Access Bank as a case study. While acquisitions are often driven by financial and operational synergies, the overlooked dimension of cultural harmonization remains a major determinant of success or failure. Using a qualitative case study approach, this research highlights the complexities associated with merging two distinct organizational cultures—Access Bank's performance-driven and hierarchical model and Diamond Bank's relational, customer-centric ethos. Findings reveal that cultural harmonization efforts centered on structural alignment, such as unified human resource policies and compensation systems, but neglected critical emotional and relational dynamics.

Diamond Bank employees reported feelings of alienation and acculturation stress, resulting from perceived dominance of Access Bank’s work culture. Key challenges included lack of inclusivity, transparency gaps in communication, and resistance to change, which compounded difficulties in achieving a cohesive post-merger harmonization. Despite these challenges, strategies such as cross-functional workshops, leadership dialogues, and integration programmes offered opportunities for mutual understanding. However, their implementation fell short of fostering an inclusive, balanced cultural framework. The study concludes that cultural harmonization strategies employed during the merger focused heavily on structural harmonization—aligning human resource policies, compensation systems, and operational frameworks.

While necessary, this approach neglected the emotional and relational dimensions of cultural integration. Employee voices and organizational values from Diamond Bank were perceived as undervalued, resulting in dissatisfaction, alienation, and resistance to change. The study recommends adopting a participatory, third-culture approach that combines the strengths of both entities, prioritizing employee engagement, transparent communication, and leadership alignment as critical components for successful cultural integration.