In this study, merger-related productivity growth in a Canadian bank is investigated using non-parametric frontier techniques. Employing Data Envelopment Analysis, efficiency improvements achieved through the merging of retail-banking branches are assessed by (i) calculating the pre-merger branch efficiency in 1999--2000, (ii) calculating the post-merger branch efficiency in 2002--2003, and (iii) comparing the pre- and post-merger results. Malmquist indices are calculated and decomposed to measure technical efficiency change and technological change. The results indicate that, on average, branches experienced technical efficiency gains after the merger. Also, in the majority of cases, branches that were closed and merged with surviving branches became more scale efficient. Moreover, branches that were directly affected by merger activities experienced greater efficiency and productivity gains than branches that were not directly affected. The results suggest that the newly merged bank has been able to capitalize on the opportunity to reduce operating costs, optimally re-allocate staff and realize synergies.