Changes in the classification of autism and Asperger's syndrome led to changes in social perception of ASD. Since last criteria, studies indicate higher levels of stigma towards ASD than towards Asperger's. These prejudices are barriers to inclusive education. Thus, it is relevant (1) to evaluate pre-service teachers' self-efficacy towards the label of ASD; (2) to evaluate pre-service teachers' self-efficacy towards the label of Asperger's; and (3) to compare those results to analyse whether the use of different diagnostic labels brings about different levels of self-efficacy. One hundred and eighty-six primary education pre-service teachers participated in the current study. Two adaptations of the Autism Self-Efficacy Scale for Teachers (ASSET) were used: a version with the label of 'ASD' (n = 96) and another for 'Asperger's' (n = 90). The scores obtained by the group asked about ASD were high according to the ASSET score range, while the scores obtained by the group asked about Asperger's were medium. After comparing the results, participants asked about the label ASD showed higher levels of self-efficacy than participants asked about Asperger's. These results could be a consequence of the consolidation of the ASD diagnosis among society and the higher presence of children with ASD in schools and cultural products, among other factors.