Relationships are formed to meet individual goals, and one consequence of this joint effort towards mutual goal fulfillment will be a level of relationship harmony achieved between the interaction partners. The present study investigated the personality correlates associated with the achievement of relationship harmony in a group setting and its consequences for group performance. Students from a social psychology course formed groups for completing task assignments. After a 3‐month collaboration, each student evaluated his or her level of relationship harmony attained with each of his or her other group members. It was found that a member’s agreeableness positively predicted his or her achievement of relationship harmony in the group, but that conscientiousness and openness to experience had detrimental effects on the relationship harmony achieved with other group members. A group whose members attained higher relationship harmony performed better on its group assignments, suggesting that relationship harmony among members of a group might have beneficial effects on group processes like performance focus and shared exchange at least in a collectivist, Chinese culture.