Growing evidence shows that a student's growth mindset (the belief that intelligence is malleable) can benefit their academic achievement. However, due to limited information, little is known about how a teachers' growth mindset affects their students' academic achievement. In this paper, we study the impact of teacher growth mindset on academic achievement for a nationwide sample of 8th and 10th grade students in Chile in 2017. Using a student fixed effect model that exploits data from two subject teachers for each student, we find that being assigned to a teacher with a growth mindset increases standardized test scores by approximately 0.02 standard deviations, with larger effects on students with high GPAs and particularly on students in low socioeconomic schools. [Funding for this report was provided by Fondecyt Inicio, the Centre for Social Conflict and Cohesion Studies (COES), the Millennium Nucleus of Social Development (DESOC), and the Chilean National Council of Education (CNED).]