This study investigated 11 Taiwanese elementary school English teachers' designs and implementations of design thinking lessons. The analysis of qualitative data (lesson plans, observations, interviews) and quantitative data (questionnaire) reached the following major findings. Firstly, English teachers considered their design thinking instruction as effective, because they endeavoured to create authentic contexts relevant to their learners and employ group discussion and oral presentations. Secondly, English teachers regarded leading learners to discuss solutions and foster their critical thinking, learners' limited English abilities, and time constraints as the biggest challenges. Suggestions on effective designs and implementations of design thinking mindsets into English courses were provided.