Assessment is one of the most contested topics in Content and Language Integrated Learning (CLIL) because of the duality between content and language, and the lack of official guidelines and research on this matter. Furthermore, as CLIL is an umbrella term portraying different realities, it is essential to consider the educational contexts in which this methodological approach is set. These various settings make each CLIL program unique concerning general aspects such as the educational level, the amount of exposure to the foreign language, the students' age and level in the foreign language, and the different subjects being taught through it. The aim of this article is to discuss existing research on CLIL assessment and to offer a preliminary functional model for practitioners to deal with language issues. By analyzing the literature in a systematic way, the concepts of discrete and integrated assessment are revisited, and a closer look at the importance of considering students' limited language proficiency and errors are also considered. It is hoped that the suggested functional model and the recommendations derived from it can serve as an aid to teachers in assessing language in a variety of CLIL subjects and contexts.