Past studies have shown that individuals with higher avoidant attachments have satisfying relationships with romantic partners when they outperform their partners. However, these findings have not been examined in other cultural contexts or other intimate relationships (e.g., relationships with best friends). In this study, we investigated whether the relation between avoidance attachment and individuals’ psychological closeness with their romantic partners and best friends would be moderated by social comparison. Sixty-eight Chinese youths in romantic relationships and 120 Chinese youths in close friendships participated in the study. Participants were asked to complete a series of self-report questionnaires regarding avoidance attachment and psychological closeness and to recall experiences about social comparisons in their close relations with romantic partners or best friends using an open-ended form. Results suggested that compared to those lower in avoidance, individuals higher in avoidance had less closeness with their romantic partners after social comparisons. Moreover, these highly avoidant individuals tended to have less closeness with their romantic patterns after an upward comparison than a downward comparison. However, unlike in romantic relationships, highly avoidantly attached participants were not significantly different from those less in avoidance in the closeness with their best friends following social comparisons. Furthermore, although both individuals who are higher and lower in avoidance experienced changes in their closeness with best friends following upward and downward comparisons, these changes were not significant.