Lay abstract: Lying, a universal social behaviour, is frequent in everyday communication. Due to differences in social communication and experiences, autistic and non-autistic adults may react differently in situations where they must decide whether to lie or tell the truth. We investigated whether autistic and non-autistic adults differ in their general lying behaviour (e.g. how often they lie) and their likelihood of lying in a range of hypothetical social scenarios with different motivations (why people lie - to benefit or protect) and orientations (who people lie for; themselves, other, a group). We also examined participants' emotional experiences of lying and truth-telling. We found that autistic and non-autistic adults' general lying frequencies and emotional experiences were similar. However, the social scenario responses revealed that autistic adults would be less likely to lie to benefit or protect a social group they are part of. Moreover, autistic adults indicated that they would find lying more difficult across all social scenarios, experience more guilt, and would be less confident that their lie would be believed. This research highlights how autistic adults' lying may be context-dependent and considers how a reduction in the likelihood of lying for their social group could increase strain on autistic adults' social relationships.