Emotional acceptance, alexithymia, and intolerance of uncertainty (IU) contribute to anxiety disorders in neurotypical populations. Their association with anxiety in people diagnosed with autism spectrum disorder (ASD) has not been studied. We aimed to model the contributions of these constructs on the relationship between dimensional measures of autism and anxiety. Participants were 151 adults recruited from 2 sites, including those diagnosed with ASD (n = 76) and a matched comparison group (n = 75). All participants completed a battery of questionnaires measuring core autism symptoms, anxiety, emotional acceptance, alexithymia, and intolerance of uncertainty. Structural equation modeling with mediation was used to examine directional relationships among these variables. Autism symptoms directly predicted less emotional acceptance and increased alexithymia and IU. Alexithymia and acceptance were shown to explain 64% of the effect between autism symptom severity and anxiety level. This suggests that people with ASD experience increased levels of anxiety because they are more likely to react aversively to their emotional experiences, while lacking the ability to identify and understand their emotions. Developing and implementing mindfulness-based interventions aimed at assuaging alexithymia and IU, while increasing emotional acceptance, may be especially helpful in treating anxiety in ASD.