This study’s goal is to investigate and better understand the issues connected with project teams’ building in enterprise system (ES) implementation. The analysis builds on two-phased research conducted among two groups of enterprises introducing ES into their organizations. The investigated issues include the project team composition, the involvement of a system provider’s representatives, project manager’s characteristics, and the composition of a steering committee. The defined issues were investigated in an exploratory manner during the first phase of the study. Next, in the second phase, this study seeks to discover their impact on the ES adoption success using multiple regression techniques. The main findings suggest the importance of a complete implementation team building and the necessity of keeping a high status of the project by appointing people holding high managerial positions within the company. Finally, recommendations regarding the implementation team composition conclude the paper.