The aim of this study was to empirically consolidate previous friendship measures in order to identify a set of items to include in a tool for assessing positive and negative qualities of adolescents’ friendships. Existing self-report measures were identified and 91 items were selected from the measures. Following a pilot study undertaken to reduce the number of items for use in a larger study, the primary study included 415 Australian adolescents (249 boys and 166 girls, aged 12–17 years) who completed a questionnaire at school. The questionnaire included a reduced set of 47 of the 91 items. Exploratory factor analysis was conducted with 50% of the sample (n = 208). In the final factor analysis, 26 items loaded highly on one of four factors. The factors were labeled emotional support, positive interactions, coercive power, and conditional social regard. The factor structure was confirmed with the other 50% of the sample (n = 207). This confirmatory factor model had a good fit to the data and the four subscales on the new Adolescent Friendship Structure Inventory (AFSI) had sound inter-item correlations. In addition, the AFSI subscales were validated against a measure of friendship satisfaction, with all four subscales associated with satisfaction in the expected direction.