This study used eye-tracking to examine how 20-month-old toddlers with autism spectrum disorder (ASD) (n = 28), typical development (TD) (n = 34), and non-autistic developmental delays (DD) (n = 16) monitored the activities occurring in a context of an adult-child play interaction. Toddlers with ASD, in comparison to control groups, showed less attention to the activities of others and focused more on background objects (e.g., toys). In addition, while all groups spent the same time overall looking at people, toddlers with ASD looked less at people's heads and more at their bodies. In ASD, these patterns were associated with cognitive deficits and greater autism severity. These results suggest that the monitoring of the social activities of others is disrupted early in the developmental progression of autism, limiting future avenues for observational learning.