The crucial role of language mastery for science learning has been gaining increasing recognition, up to the point of being often viewed as the possible single major factor determining the learning quality and efficiency. The present chapter focuses on the role of language mastery for chemistry learning, offering a broad spectrum of information from direct experience at the tertiary level to document the impact of inadequacies in language-mastery extent and depth. This analysis also provides indications on the language-mastery sophistication level needed for successful chemistry learning. Considerations on the importance of mother tongue instruction are added because of the essential role of the mother tongue for clearer conceptual understanding and for building language-mastery, including the ability to express acquired knowledge through other languages. The envisaged ‘way forward’ to overcome diagnosed challenges entails the integration of language components into chemistry teaching in such a way that language analysis (analysis of the relationships between chemistry concepts and the way in which they are expressed) becomes an explicit tool for the clarification of chemistry concepts and for active learning.