Background: Research exploring the context in which ASD and offending are associated is limited, despite stereotyped perceptions that individuals with ASD are more violent than their typically developing peers. To address this gap, this research explored the influence of ASD, mental health and behavioural presentation, adverse childhood experiences, and demographic characteristics on offending presentations in a forensic youth sample. Methods: This was a cross-sectional study of a retrospective cohort, utilising secondary data of 327 young people from a forensic London-based service (83% male, M_age = 14.9 years old, SD = 1.90). Results: One hundred forty-two of these young people presented with either confirmed or suspected ASD diagnoses (83.8% male, M_age = 14.8 years old, SD = 1.84). Five offending categories (violence, sexually harmful behaviour, drug possession/supply, gang involvement, theft) and 32 offending behaviours were analysed in total. Poisson and negative binomial regression analyses indicated that ASD traits only increased the rate ratio of violent offences (p = 0.036) and gang involvement (p = 0.002). The use of substances significantly increased the rate ratio of theft (p = 0.012), gang involvement (p = 0.004), and drug possession/supply (p = 0.012). Conclusions: Our findings suggest that ASD, in the context of substance use, may increase a young person’s risk for more variable violent offences or gang involvement. Findings are discussed in the context of current research and recommendations for clinical practice and future research are made.