<p>According to the Cognitive Load Theory as well as research regarding cognitive development in childhood, the use of instructional videos in primary education brings challenges. Particularly, primary students should be supported to maintain their attention on the instructional information. In the current experiment, performing a mindfulness meditation before video reception was investigated as a short intervention to promote subsequent learning-relevant processes. Overall, 180 students were either assigned to the meditation or filler task condition. We furthermore explored prior knowledge in the instructional topic and thus, quasi-experimental divided the participants into 3rd and 4th graders. Students learned the process of division of long numbers without a calculator by watching an instructional video. Results revealed that the mindfulness meditation enhanced mental effort as well as retention performance. Furthermore, 3rd graders particularly benefited from the meditation because, in contrast to the 4th graders, attention processes and germane processes were particularly promoted. Results are discussed by creating synergies between the Cognitive Load Theory and cognitive development research as well as research regarding meditational practices in educational contexts.</p>