This study aimed to understand the effect of task motivation on online group creative performance and interpersonal interaction. A total of 150 university students were recruited to collaborate online on creativity tasks in dyads. The members' task motivation was manipulated, resulting in three groups that differed in their motivation composition. Ratings of creative performance (fluency and originality), hemodynamic inter-brain synchronization, and lag sequential analysis were compared among the three groups. The results showed that groups comprising two highly motivated members conducted an efficient communication mode and achieved the best creative performance. Contrastingly, groups composed of one high- and one low-motivation member demonstrated the closest interpersonal interaction among members. The findings of this study suggest that it is essential to ensure that every member is highly motivated to improve creative performance in online groups. However, this may result in reduced interpersonal interaction.