First impressions of autistic individuals are more negative than those of their non-autistic peers. There is also a higher prevalence of gender diversity among autistic than non-autistic individuals. No studies to date have investigated the impact of perceived gender on social first impressions of autistic and non-autistic individuals. In this study, adult participants (i.e., undergraduate students) watched sixty 7-10 s video clips of 15 non-autistic females, 15 non-autistic males, 15 autistic females, and 15 autistic males engaging in a "get-to-know-you" conversation (video of participant only). Adult participants provided social first impression ratings and perceptions of gender (femininity, masculinity, and other/neither) for each participant using slider bars. Results showed that autistic youth received lower social ratings than non-autistic youth, and that girls overall were rated more favorably than boys. However, for autistic girls there was a significant correlation between perceived gender and social first impressions that did not exist in the other three groups. Specifically, autistic girls who were perceived as less feminine and more other/neither were also rated lower on social first impressions. These novel findings highlight a double penalty for autistic girls who diverge from societal expectations about both gender and typical social behavior.