Improving physical activity (PA) levels in autistic adults is an important population health goal. Limiting efforts to achieve this goal is an incomplete understanding of the barriers to PA in this high-risk group. This study utilized cross-sectional data collected via an electronic survey from 253 autistic adults aged 18-50 years to examine their perceived barriers to PA, how PA barriers differed by demographic factors, and the relationship between PA barriers and meeting PA guidelines. The Barriers to Physical Activity scale assessed the independent variable. Lack of motivation to exercise, perceiving exercise as boring, and lack of transportation were the most strongly endorsed barriers to PA. Participants who reported these barriers were significantly less likely ([less than or equal to] 50%) to meet PA guidelines.