Year 12 students are in a transitional year, academically and interpersonally. This year involves many changes and the need for students to make future plans, which can be a challenge for many adolescents. During times of transition, such as Year 12, expectations and beliefs about relationships and the relational self (i.e., attachment patterns) may undergo changes. Identifying attachment patterns among Australian Year 12 students was the first aim of this 6-month longitudinal study (N = 130, M age = 16.4). A second aim of this study was to determine correlates of attachment change and stability. These correlates included psychological symptoms, loneliness, rejection sensitivity, social competence, and social support. Using an adolescent version of Bartholomew and Horowitz’s (1991) Relationship Questionnaire, self-reported attachment style showed some change, with 36% of adolescents changing attachment style category during the study. Adolescents were classified into groups based on their attachment styles at the two assessments. Groups included adolescents who were stably insecure, stably insecure, changed to insecure and changed to insecure. When groups were compared, most hypothesised differences were found. First, stably insecure individuals had the most positive psychological functioning, and they had the most stable and positive perceptions of self and others when compared to other groups. Second, stably insecure adolescents were less well-adjusted than others. Third, the changed to insecure group showed improvements in functioning over time. However, it was not clear that adjustment had declined in the changed to insecure group.