Background: Previous research has shown that pre-service teachers have low responsibility for student motivation and feel underprepared to deal with motivational issues. As an extension, researchers have designed interventions to shift teachers' beliefs about motivation or equip them with approaches to instruction, but never both. Aims: Following best practices for motivation interventions, we created a one-session online intervention and tested its efficacy to shift pre-service teachers' self-reported beliefs and approaches to instruction to be more supportive of student motivation. The intervention included priming, materials designed for mindsets and/or for approaches to instruction, a consolidation activity, and take-home materials. Sample: A convenience sample of 384 pre-service teachers from one Canadian university participated. Methods: We embedded an experimental design into multiple sections of a required assessment course. After completing a pre-test, participants were randomly assigned to one of four conditions: beliefs-only, approaches-only, combined beliefs and approaches, or control. After completing the online module, students received a lecture on assessment practices and motivation. Results: The results from our MANCOVA showed that pre-service teachers who participated in the beliefs-only condition reported increased levels of responsibility for student motivation, more growth mindset beliefs, and less fixed mindset beliefs than participants in the other conditions. The approaches-only condition did not influence self-reported mastery or performance approaches to instruction and the combined condition had no effect on beliefs or approaches. Conclusions: We discuss the implications for educating pre-service teachers about student motivation and suggest that beliefs and approaches to instruction need to be addressed separately.