The ability to represent mental states (theory of mind [ToM]) is crucial in understanding individual differences in social ability and social impairments evident in conditions such as autism spectrum disorder (ASD). The Reading the Mind in the Eyes Test (RMET) is a popular measure of ToM ability, validated in part by the poor performance of those with ASD. However, the RMET requires recognition of facial emotion, which is impaired in those with alexithymia, which frequently co-occurs with ASD. Thus, it is unclear whether the RMET indexes emotion recognition, associated with alexithymia, or ToM, associated with ASD. We therefore investigated the independent contributions of ASD and alexithymia to performance on the RMET. ASD and alexithymia-matched control participants did not differ on RMET performance, whereas ASD participants demonstrated impaired performance on an alternative test of ToM, the Movie for Assessment of Social Cognition (MASC). Furthermore, alexithymia, but not ASD diagnosis, significantly influenced RMET performance but did not affect MASC performance. These results suggest that the RMET measures emotion recognition rather than ToM ability and support the alexithymia hypothesis of emotion-related deficits in ASD.