Understanding ourselves within our peer environment is an important component of self-development during adolescence, the period of life between the onset of puberty and adulthood (between ages 10 and 24 years). We used a self-appraisal paradigm to investigate cross-sectionally the relationship between perceived friendship quality and self-judgements in adolescent girls. One hundred and sixty-three girls (9-15 years), recruited from London, United Kingdom, rated how well a set of positive and negative adjectives described themselves, or a chosen familiar other. Participants also completed a self-report friendship quality questionnaire. Higher perceived friendship quality predicted lower negative self-judgements and higher positive self-judgements. These relationships did not change across the age range tested, but there was an overall decrease in positivity effect (higher positive judgements compared to negative judgements) with age. These findings highlight the importance of investigating how different components of peer relationships are related to self-concept development in adolescence.