The construction of scientific explanations is recognised by science education researchers and curriculum developers as one of the core epistemic practices in which students should acquire proficiency. However, little is known about the knowledge and skills that teachers must and do put into practice to successfully engage their students in building explanations. Therefore, an exploratory study was conducted to analyse the instructional strategies that two secondary science teachers used to promote students' participation in the elaboration of scientific explanations. To this end, a multi-method approach was used for data collection, which included observations and semi-structured interviews. Data analysis was carried out in two stages: the first stage was aimed at inductively encoding the participants' interactions and discursive actions, and the second stage was aimed at performing a cross-case examination of them through constant comparative analysis. Codes were refined and clustered into seven categories. The results show that teachers quite frequently use micro strategies to interact with and guide students in explanatory episodes, but very rarely structure them into/within a complete instructional sequence to purposely promote the formulation of scientific explanations. This suggests the need to promote an explicit and conscious science teacher training to enrich their knowledge of instructional strategies for fostering and scaffolding students' explanations.