A qualitative study was made of how the learning-to-learn competence is favoured in prospective primary teachers when they participate in an experimental activity (ExA). The ExA was on the germination of seeds. Its objective was for the prospective teachers to learn how to (i) design and execute a school scientific inquiry, and (ii) reflect metacognitively about their experience with the ExA and what they had learnt. This latter objective is analysed in the present study. To this end, a category-descriptor instrument was designed for the learning-to-learn competence. This allowed the moments and actions to be analysed, as well as the prospective teachers' cognitive and metacognitive strategies during the ExA. The participants were organised into small work groups, and the information analysed was drawn from the records of the ExA in the notebooks which those groups prepared. In general, the results are indicative of the positive effect of the proposed ExA on the development of cognitive and metacognitive strategies in the prospective teachers' learning processes. Especially important were the moments of idea confrontation, reflection, and whole-class sharing since they let the prospective teachers become aware of and control these strategies. The scope, limitations, and implications of the study are discussed.