There is an on-going debate over the long-term value propositions of enterprise systems (ES) for competitive advantage, with many arguing that ES have lost their potential to contribute to competitive advantage in the contemporary hyper-competitive markets. While acknowledging that an ES is a valuable, rare and non-substitutable resource that is common to all competitors, it is further questionable how ES contribute to competitive advantage. Using the fourth characteristic of the resource-based view, we investigate how inimitability of ES can contribute to competitiveness. Using qualitative evidence from nine case studies this study derives three conditions that facilitate ES to be inimitable.