People with autism and higher levels of autistic traits often have difficulty interpreting facial emotion. Research has commonly investigated the association between autistic traits and expression labeling ability. Here, we investigated the association between two relatively understudied abilities, namely, judging whether expressions reflect genuine emotion, and using expressions to make social approach judgements, in a nonclinical sample of undergraduates at an Australian university (N = 149; data collected during 2018). Autistic traits were associated with more difficulty discriminating genuineness and less typical social approach judgements. Importantly, we also investigated whether these associations could be explained by the co-occurring personality trait alexithymia, which describes a difficulty interpreting one's own emotions. Alexithymia is hypothesized to be the source of many emotional difficulties experienced by autistic people and often accounts for expression labeling difficulties associated with autism and autistic traits. In contrast, the current results provided no evidence that alexithymia is associated with differences in genuineness discrimination and social approach judgements. Rather, differences varied as a function of individual differences in specific domains of autistic traits. More autistic-like social skills and communication predicted greater difficulty in genuineness discrimination, and more autistic-like social skills and attention to details and patterns predicted differences in approach judgements. These findings suggest that difficulties in these areas are likely to be better understood as features of the autism phenotype than of alexithymia. Finally, results highlight the importance of considering the authenticity of emotional expressions, with associations between differences in approach judgements being more pronounced for genuine emotional expressions. (PsycInfo Database Record (c) 2024 APA, all rights reserved).