Abstract Managing classrooms with groupwork activities has been popular in EFL context. However, there are groups that work effectively while some others are not able to achieve the desired results. This study attempts to examine how the group members’personality traits affect group’s speaking performance in three English classes for non-English major students. A questionnaire was distributed to 85 participants at the beginning of the term in order to collect data about their personnality traits. Then the author formed three types of groups of four or five students: groups with extroverts members, groups with introvert members and groups with mixt characteristics. She assigned one speaking topic per week to all the groups. A survey was also conducted at the end of the term in order to investigate students’ attitudes toward the formation of the types of groups and group work. The classroom observation and students’ group speaking performance indicated that the groups with extroverts performed better than the other ones. The data collected also showed that students personality traits effected group work performance as well.