The brain generates predictions to prepare for upcoming events. As life is not always 100% predictable, it also estimates a level of certainty for these predictions based on their likelihood. Given that autistic individuals resist even small changes in everyday life, we hypothesized impaired tuning of prediction certainty in autism. To study this, EEG was recorded from adolescents and young adults with autism, and age-and IQ-matched controls while they performed a probabilistic cued target detection task in which cue validity was parametrically manipulated. A fully predictable condition (100% cue validity) was contrasted with less predictable conditions (84%, 67%, and 33% cue validity). The contingent negative variation (CNV), a brain response associated with the anticipation of a predictable target, was examined to test the influence of cue validity on target predictions. Whereas the CNV systematically modulated by cue validity in the control group, this was not the case for the autism group. In contrast, intact modulation of the target P3 response by cue validity indicated that stimulus statistics are registered in a typical manner in autism. This suggests that in autism target statistics were registered but were not effectively applied to modulate expectations (eg, certainty) of upcoming predictable stimuli. This adds to our understanding of differences in predictive processing in autism and suggests that the tuning of prediction certainty is particularly vulnerable in this population.