This study tests a theoretical model developed to investigate the impact of assimilation of commercial open source enterprise resource planning software (COSES) in small and medium sized enterprises (SMEs). Specifically, the model explains how the top management team’s (TMT’s) information technology (IT) knowledge and experience impact both assimilation and firm performance. The hypotheses were tested using survey data from SMEs that have implemented COSES. Results from structural equation modeling suggest that SMEs benefit, through higher levels of assimilation and performance, from adopting innovative enterprise resource planning (ERP) systems such as COSES when they have a TMT that has experience with and is knowledgeable about technology. The study also highlights the importance of the TMT in facilitating IT assimilation.