It has been argued that metacognition and mindreading rely on the same cognitive processes (Carruthers in The opacity of mind: an integrative theory of self-knowledge, Oxford University Press, Oxford, 2011). It is widely accepted that mindreading is diminished among individuals diagnosed with autism (Brunsdon and Happé in Autism 18(1):17-30, 2014), however, little is known about metacognition. This study examined metacognition in relation to mindreading and autism using post-decision wagering. Results from a student sample showed negative associations between autism traits and metacognitive accuracy, and metacognitive reaction times and mindreading. These findings were replicated in a general population sample, providing evidence of a reliable association between metacognition, mindreading and autism traits. However, adults diagnosed with autism showed equivalent levels of metacognitive accuracy to age- and IQ-matched comparison participants, albeit only with an overall increase in meta-level processing time.