For undergraduate students interested in STEM fields, participating in a research lab with a faculty mentor is an important developmental step for their future careers. However, autistic college students often feel devalued in academic contexts in general and experience interactions with faculty members who know little about autism or how to be inclusive to their needs. Informed by the double empathy theoretical approach to studying autism, our aim is to elucidate the areas of knowledge, skills, behaviors, and attitudes where STEM faculty most need to improve to facilitate mutual understanding within STEM research labs. We conducted focus groups and interviews with 16 autistic students (graduate and undergraduate) who had experience in a STEM research lab or were interested in STEM and 14 STEM faculty and lab staff. We analyzed the qualitative data using a training needs assessment approach, in which we focused on key gaps between what autistic students reported wanting faculty to know/ be able to do and what STEM faculty reported knowing/ doing currently. We identified three overarching themes that each contained several key targets for learning: awareness of autistic experiences (e.g., understanding the non-linear spectrum of autism and the diversity of autistic individuals), readiness to implement accommodations (e.g., normalizing the accommodations process in the lab), and commitment to an inclusive lab culture (e.g., providing clear norms and expectations). The three “ARC” themes can help prioritize training content for labs, as well as lab policies and procedures, to ensure that non-autistic individuals are putting forth appropriate efforts toward ensuring mutual understanding through having basic knowledge of autism, normalized accommodations processes, and specific affirming lab practices.