Efficacious, effective teaching markedly impacts students' learning and academic achievement. How can we motivate teachers to feel efficacious, and hence teach effectively, amidst challenges? Our research introduced and tested the role of a 'teacher strategic mindset'--an orientation towards construing teaching challenges as opportunities to step back and consider new, potentially more effective strategies. Teachers who had this strategic mindset felt more efficacious, and in turn, were more likely to report engaging in self-regulated behaviours and metacognition (Study 1). Moreover, instilling this teacher strategic mindset through a brief, online intervention causally increased teachers' reported efficacy, and their intentions to engage in self-regulated behaviours and metacognition--specifically among those who had a growth mindset (Study 2). Beyond subject matter knowledge and pedagogical skills, a teacher strategic mindset has practical value in motivating efficacious and thus effective teaching.