Early science instruction is important in order to lay a firm basis for learning scientific concepts and scientific thinking. In addition, young children enjoy science. However, science plays only a minor role in the kindergarten curriculum. It has been reported that teachers feel they need to prioritize language and literacy practices over science. In this paper, we investigate whether science lessons might be integrated with learning the language functional for school: academic language. The occurrence of scientific reasoning and sophisticated vocabulary in brief science lessons with 5-year-olds is evaluated. The aim of the study was twofold: first, to explore the nature of kindergarten science discourse without any researcher directions (pre-intervention observation). Second, in a randomized control trial, we evaluated the effect on science discourse of a brief teacher training session focused on academic language awareness. The science lessons focussed on air pressure and mirror reflection. Analyses showed that teachers from the intervention group increased their use of scientific reasoning and of domain-specific academic words in their science discourse, compared to the control group. For the use of general academic words and for lexical diversity, the effect was task-specific: these dependent measures only increased during the air pressure task. Implications of the study include the need to increase teachers' awareness of possibilities to combine early science instruction and academic language learning.