This article sets out to broaden the understanding of foreign language self-concept in CLIL context. The few existing studies on self-concept in CLIL have been quantitative and provided somewhat discrepant results, highlighting the need for approaching the topic qualitatively. The data of the present study are in-depth interviews with 24 former Finnish CLIL pupils who retrospectively reflected on their CLIL experiences. The participants had received English-medium CLIL for nine years during their comprehensive school in the 1990s. The data were analyzed qualitatively using thematic analysis. The participants generally felt that CLIL had had a significant role in contributing to their very positive English language self-concept. Most reported being highly confident language users who had not experienced any language anxiety in English. However, some participants’ self-concept had oscillated throughout the years. The participants put a lot of emphasis on social comparisons, external feedback and the early start of CLIL in forming their positive English self-concept. The participants’ self-concepts in other foreign languages seemed to be more negative. The results indicate that early and fairly moderate CLIL has potential in creating a positive target language self-concept, which encourages to adopt CLIL methodology also to mainstream language education.