Interpretation biases, in which ambiguous information is interpreted negatively, have been hypothesized to place adolescent females at greater risk of developing anxiety and mood disorders than same‐aged males. We tested the hypothesis that adolescent girls interpret ambiguous scenarios more negatively, and/or less positively, than same‐aged males using the Adolescent Interpretation and Belief Questionnaire ( N = 67, 11–15 years old). We also tested whether adolescent girls and boys differed in judging positive or negative interpretations to be more believable and whether the scenario content (social vs. non‐social) affected any sex difference in interpretation bias. The results showed that girls had higher average negative interpretation scores than boys, with no sex differences in positive interpretation scores. Girls and boys did not differ on which interpretation they found to be most believable. Both sexes reported that positive interpretations were less likely to come to mind, and were less believable, for social than for non‐social scenarios. These results provide preliminary evidence for sex differences in interpretation biases in adolescence and support the hypothesis that social scenarios are a specific source of anxiety to this age group. A greater understanding of the aetiology of interpretation biases will potentially enhance sex‐ and age‐specific interventions for anxiety and mood disorders.