Co-creation communities allow companies to utilize consumers’ creative thinking in the innovation process. This paper seeks to understand the role of sentiment in user co-creation. The results suggest that management style can affect the success of co-creation communities. Specific employees’ communication styles, the sentiments embedded in the messages, task-oriented content, and proactiveness can all influence individual user sentiment. The aggregation of these individual user sentiments, resulting in collective sentiments, affects co-creation performance. Increasing negative collective sentiment results in decreased subsequent creativity and increased future participation. Conversely, growing positive collective sentiment leads to a lower level of participation.