We conducted a study to explore whether or not 3 of the Big Five personality traits – namely, extraversion, neuroticism, and psychoticism – moderated the effects of peer attachment on loneliness among a group of adolescents who were deaf. The participants were 98 Chinese adolescents who were pupils at 5 special schools for those who are deaf. They completed anonymous questionnaires regarding peer attachment (the Inventory of Parent and Peer Attachment-Revised), personality (the Junior Eysenck Personality Questionnaire), and loneliness (the Loneliness and Social Dissatisfaction Questionnaire). The results showed that extraversion moderated the relationship between peer attachment and loneliness, but neither neuroticism nor psychoticism had a moderating effect. Specifically, peer attachment predicted loneliness more strongly for highly extraverted adolescents than for their introverted peers. These findings illustrate that the effects of peer attachment on a subjective mental state varied considerably across this group of adolescents who were deaf, depending on the level of extraversion of each individual.