Employment interviews can be challenging for autistic people. In addition to standard interview procedures often being inaccessible, features associated with autism (including atypical emotional expression, eye-contact, and gestures) may lead to negative first impressions. Research using vignettes and 'thin slices' of communication indicate that perceptions of an autistic individual can be improved when their autism diagnosis is disclosed. Here, we examined the impact of diagnostic disclosure on judgements of autistic adults undergoing an entire mock employment interview. A total of 119 participants (known as 'raters') watched a video of an autistic candidate's mock employment interview, after which they provided overall impressions of the candidate on factors such as confidence, motivation, and knowledgeability. Raters were either (1) unaware of the interviewee's diagnosis, (2) aware of their diagnosis, or (3) aware of their diagnosis and provided with information about autism. Results indicate that diagnostic disclosure improved perceptions of autistic candidates across all dimensions compared to when raters were unaware of their diagnosis. The provision of additional information about the diagnosis did not further improve ratings. The findings have important implications for employers and autistic people, who should consider the potential impact of diagnostic disclosure prior to interviewing for a role.