This article draws upon one aspect of a larger study that aimed at exploring the relationship between decontextualization skills developed by teenagers in a trilingual context involving Arabic (L1), French (L2) and English (L3). We examined the decontextualization skills (DS) of 195 students aged 16–17 years through their written definitions in L1, L2 and L3. Our objective was to investigate whether these skills were related between the three languages and whether language distance and language proficiency had an effect on the results. DS proved to be interdependent across languages and independent of language distance. Language proficiency was a significant predictor of DS without being their mainstay. The interdependence of DS across languages supports the interdependence hypothesis (Cummins, 1991) according to which there is an inherent cognitive/academic proficiency common across languages despite their different surface aspects.