On average, groups of autistic individuals are more likely than groups of non-autistic individuals to exhibit unconventional conversational behaviours. We examined autistic and non-autistic children's social impressions of unconventional responding, as well as actual conversational behaviours in the same participants. Across two studies, 36 autistic and 36 non-autistic matched 9-13-year-olds listened to conversational vignettes which manipulated the relevance and timing of responses produced by the speaker. They then rated the speaker's social desirability. We also measured the content and latency of the same children's conversational responses. Autistic children aligned with their non-autistic peers in indicating that they were less likely to befriend, or enjoy interacting with, a speaker who provided off-topic or delayed responses. However, the same autistic children provided more off-topic, and fewer topic-continuing, conversational responses than their non-autistic counterparts. These findings suggest that displaying unconventional conversational behaviours may act as a barrier to friendship or inclusion for autistic children, even when socialising with other autistic peers.