ABSTRACTCentral sensitivity syndromes (CSSs) are a group of health conditions thought to include an underlying sensitisation of the central nervous system. Evidence suggests autistic adults experience poorer physical health than the general population and are more likely to have a CSS. This study examined CSS diagnoses and symptoms in autistic and non‐autistic adults, to determine whether CSS symptoms were related to autistic traits, mental health, sensory sensitivity, age or gender. Participants included 534 adults with clinical diagnoses of autism, CSS, both diagnoses or neither (i.e., comparison group), who were recruited through social media, support groups and institutional affiliations. Participants completed online self‐report validated questionnaires, including the Autism Spectrum Quotient (AQ), Central Sensitization Inventory (CSI), Sensory Perception Quotient (SPQ), and the PHQ‐9 and GAD‐7. Autistic people without a diagnosed CSS reported significantly more CSS symptoms than the comparison group, with a mean score above the clinical cut‐off. Non‐autistic participants with a CSS had significantly more autistic traits than the comparison group. Autistic people with a CSS reported the most sensory sensitivity, with autism only and CSS only groups reporting similar levels of sensory sensitivity and all diagnostic groups reporting more sensory sensitivity than the comparison group. Sensory sensitivity, anxiety, autistic traits, age and gender were all significant predictors of CSS symptoms. The overlap in symptoms between autistic individuals and those with CSS suggests diagnostic overshadowing and possible under‐diagnosis or misdiagnosis. Furthermore, these symptoms may exacerbate or mask one another. Notwithstanding potential limitations of representativeness and selection bias, increased awareness of the association between autistic traits and CSS symptoms is important for clinicians to improve diagnostic accuracy and treatment.