This study is based on the hypothesis that group cohesion and efficacy have significant effects on the academic performance of individuals in online (virtual) education environments no less than in-person education environments. To that end, this study explores the effectiveness of group activities in a virtual classroom environment using VC (Virtual Conferencing). It is based on a hypothesis that strong group cohesion and efficacy of a learning group influence the individual academic performance. The findings are as follows. First, team-building activities conducted in an online environment can further improve the level of group efficacy. Second, group cohesion formed in the online educational environment has a positive effect on the individual academic performance. Third, group efficacy amplified through online team-building activities mediate the relationship between group cohesion and individual academic performance. The results of the study support the hypothesis that psychological group variables can also affect the individual academic performance even in online educational environments. These findings will be helpful for researchers who are interested in designing educational collaborative activities and system development for computer-supported cooperative learning (CSCL).