--- - |2 Abstract The purpose of this study was to examine the effects of four individual factors (shyness, self‐esteem, social skills, and defensive pessimism) on the formation of friendships among undergraduate students. Freshmen (N = 93) completed a questionnaire assessing their shyness, self‐esteem, social skills, and level of defensive pessimism. Then, they answered questions about interpersonal indices (number of friends, satisfaction with friendships, their willingness to continue relationships, and their feelings of interpersonal friction). After 3 months, they completed a questionnaire about their anxiety state and behavior when talking with the people they had met since university admission. Moreover, they discussed the interpersonal indices they used in a pre‐questionnaire. Path analysis indicated that shyness directly leads to having fewer friends, whereas social skills lead to having more friends through extroversive behavior. Moreover, self‐esteem was positively related to an increase in the willingness to continue relationships, and reflection and pessimistic thinking (which is one component of defensive pessimism) led to a feeling of being fatigued from the effort of considering and respecting the reactions of others. - Japanese Psychological Research, EarlyView.