Non-autistic adults often hold explicit and implicit biases toward autism that contribute to personal and professional challenges for autistic people. Although previous research indicates that non-autistic adults with higher autism knowledge and familiarity express more inclusionary attitudes, it remains unclear whether training programs designed to promote autism acceptance and understanding affect subsequent implicit and explicit biases toward autism. In this study, non-autistic adults ( N = 238) completed an autism acceptance training featuring factual information and engaging first-person narratives, a general mental health training not mentioning autism, or a no-training control, then responded to surveys assessing their autism knowledge, stigma, and impressions of autistic adults, and completed a novel implicit association task about autism. Non-autistic adults in the autism acceptance training condition reported more positive impressions of autistic adults, demonstrated fewer misconceptions and lower stigma about autism, endorsed higher expectations of autistic abilities, and expressed greater social interest in hypothetical and real autistic people. However, training had no effect on implicit biases, with non-autistic adults associating autism-related labels with unpleasant personal attributes regardless of training condition. These findings suggest that the autism acceptance training program in this study, designed to increase autism knowledge and familiarity among non-autistic people, holds promise for reducing explicit but not implicit biases toward autism. Lay abstract Autistic adults face prejudice from non-autistic people. They are often judged unfairly and left out of social activities because of their differences. This can make it difficult for autistic people to make friends and find jobs. Some training programs have tried to teach autistic people to act more like non-autistic people to help them gain acceptance. Fewer have focused on teaching non-autistic people how to be more autism friendly. In this study, we used a short training video that teaches people about autism. The video was created with the help of autistic adults and included clips of real autistic people. We found that non-autistic people who watched this video had better knowledge about autism and showed more autism-friendly attitudes than those who watched a video about mental health or those who did not watch any video. They were more open to having a relationship with an autistic person and had more positive beliefs about autism. However, our video did not affect people’s unconscious attitudes about autism. People in our study connected autism with unpleasant traits, even if they had watched the autism training video. This suggests that teaching non-autistic people about autism may promote more autism-friendly attitudes, but some beliefs may be harder to change.