The efficacy of academic mindset interventions has been demonstrated internationally and predominantly with secondary school students. Whether a mindset intervention can change the beliefs about intelligence held by Australian primary students remains unknown, as does the relationship between students’ mindsets, their academic goal orientation, and academic achievement. A mindset intervention was delivered to 43 students in mixed ability grade 5 and 6 classes in a public primary school in Sydney, Australia. The intervention was evaluated with a randomised waitlist (control) design. The intervention promoted positive change in mindset beliefs compared with the control group. Mindset beliefs were positively associated with learning goals and academic achievement and negatively associated with performance approach and avoidance goals. The efficacy of the mindset intervention for changing primary students’ beliefs about intelligence is discussed. Implications for the further development and evaluation of brief and scalable classroom intervention to promote positive academic cognitions and achievement outcomes are discussed.