In the current study, 17 pre-service teachers at (upper) secondary school level studying English as a second language within the Swedish educational system were asked to give two mini-lessons each. Both focused on the teaching of grammar, a subarea towards which many teacher trainees have especially negative feelings. The aims were to explore the extent of the learners’ pedagogical content knowledge (PCK) and to investigate if, with the help of micro-teaching, teacher feedback/feedforward and reflective writing, their pedagogical content knowledge could be strengthened further, thus giving these pre-service teachers the boost they need to address grammatical issues in their future L2 classrooms. The findings show that the pre-service teachers’ PCK was low in connection with their first mini-lesson, but that with the scaffolding devices implemented it was enhanced, the subject knowledge component proving more easily consolidated than the pedagogical content component. As many as 15 of the 17 teacher trainees displayed positive scores on both components in their second mini-lesson, the learners who did the poorest in their first mini-lesson improving the most. Great individual differences were, however, also detected among the other learners.