Anecdotal evidence suggests that autistic people experience an elevated risk of homelessness, but systematic empirical research on this topic is lacking. As a step towards filling this gap in knowledge, we conducted a preliminary investigation of the prevalence of Diagnostic and Statistical Manual of Mental Disorders (5th ed.) autism symptoms in a group of long-term homeless people. The entire caseload (N = 106) of a UK homeless outreach team was screened (excluding individuals born outside of the United Kingdom or Republic of Ireland) using an in-depth, semi-structured interview with keyworkers, based on Diagnostic and Statistical Manual of Mental Disorders (5th ed.) diagnostic criteria. This showed adequate inter-rater reliability, as well as evidence of criterion and construct validity. Of the sample, 13 people (12.3%, 95% confidence interval (7.0, 20.4)) screened positive, meeting Diagnostic and Statistical Manual of Mental Disorders (5th ed.) autism criteria by keyworker report. A further nine people (8.5%, 95% confidence interval (4.5, 15.3)) were ‘marginal’, having autistic traits that were not quite sufficient to meet Diagnostic and Statistical Manual of Mental Disorders (5th ed.) criteria. Those with elevated autistic traits, compared to those without, tended to be more socially isolated and less likely to use substances. This study has provided initial evidence that autistic traits are over-represented among homeless people and that autistic homeless people may show a distinct pattern of characteristics and needs. Further investigation is required to build upon these provisional findings.