Dataset abstract The dataset includes vocabulary test scores from 75 native Dutch speakers from Flanders (Belgium), learning both L2 French and L2 English in a CLIL (Content and Language Integrated Learning) context. CLIL refers to the teaching of subjects, such as history or economy, in a foreign language (Coyle et al. 2010). Participants were all L1 speakers of Dutch aged 12 to 14 at time of testing (28 females, 47 males). For each language, two Vocabulary Levels Tests (VLT) were administered: a reception test and a production test. In the receptive VLT, participants matched decontextualized words with definitions, while in the productive VLT, they completed words that appeared in short sentences. Both tests were additionally performed in a pre-posttest design over a 3-month-interval. Because all participants studied L2 French and L2 English simultaneously, the data allows for paired comparisons between the gain scores of the French and English tests. The full data analysis to replicate the results in Baten et al. (2020) is provided in an R Notebook. Article abstract Content and language integrated learning (CLIL) has expanded in Europe, favored by the large body of research, often showing positive effects of CLIL on L2 development. However, critical voices have recently questioned whether these positive findings apply to any language, given that most research focuses on English. Taking into account this concern, the present study investigated the (productive and receptive) vocabulary development in L2 English and L2 French of the same group of learners within a CLIL context. The aim was not to evaluate the benefits of CLIL over non-CLIL, but, instead, to examine whether vocabulary gains in CLIL learning are language-dependent. More specifically, this study included 75 Flemish eight-grade pupils who had CLIL lessons in both English and French. The results show that although the pupils have a larger English vocabulary, the level of improvement (from pretest to posttest) is not different across the languages. ...