The present study evaluated the effects of a program designed to promote a growth mindset in maths teachers (i.e., the belief that maths ability can improve through experience and learning) to enhance teaching and learning outcomes in their maths classes. The sample was composed of 155 Israeli high-school maths teachers who were randomly assigned to a one-year intervention or control condition. Growth mindset, professional well-being and emotional teaching efficacy improved significantly in the intervention group over time but did not change in the control group. Teachers' professional well-being, was associated with an increase in student grades and a decrease in class dropout rates. These findings reinforce the need to promote a growth mindset in teachers to maximise their students' potential for maths success.