International teaching assistants (ITAs) bring cultural perspectives and language diversity to university programs. However, ITAs can be underserved through traditional professional development initiatives. A mixed-reality teaching simulator module was created to attend to the unique needs of chemistry ITAs and prepare them for active learning instruction. To create the module, seven ITAs were interviewed about their professional development needs. ITAs most commonly wanted to practice asking and answering student questions, engaging disengaged or disrespectful students, and navigating language difficulties with students. The mixed-reality simulated teaching module provided opportunities for ITAs to rehearse one or more of the three focus areas. Three ITAs tested the simulator and reported that using the simulator for professional development with cultural and linguistic layers would be beneficial both to existing and new ITAs. These research findings set the foundation for generating a transformative set of training materials that institutions can use to reduce teaching anxiety and increase the effectiveness of ITAs in the classroom, thus enhancing student learning through more effective active learning instruction.