This research investigates the role of brainstorming sessions in promoting effective user participation in ERP implementation. An exploratory case study was conducted, with the data analysis based on the grounded theory approach and the findings organized in a theoretical model. Results show that brainstorming sessions were instrumental for effective user participation, resulting in high levels of users’ psychological involvement and proactive participation behaviors. Brainstorming transformed both the subject and formality of user participation, featuring the users in the center of stage to lead the reflection and sharing in a personally meaningful and relevant manner. Senior management push and consultant support were also identified as factors affecting the success of brainstorming.