Research on form focused instruction has provided support for the use of collaborative tasks in which learners focus their attention on formal aspects of language and consciously reflect on their own language use (i.e. produce language-related episodes or LREs). A strand of research on LREs in different educational contexts examines the effect of learner-internal factors, such as target language proficiency, on the amount, type and resolution of LREs. However, little is known about whether learners in content-and-language-integrated-learning (CLIL) programmes pay attention to formal aspects of language and much less about the relationship between learner proficiency and LREs. Therefore, this study investigates how learner proficiency affected the amount, type (lexical or grammatical) and outcome (correct, incorrect or unresolved) of LREs involving the English 3rd person singular marker -s produced during a dictogloss task by 12 pairs of adolescent EFL learners from a CLIL classroom. The findings revealed that there was a positive correlation between the number of LREs involving the target form and the learners' proficiency. Positive correlations were also found between learner proficiency and correctly resolved grammatical LREs involving 3rd person singular forms.