Abstract Objectives The mental and physical health profile of autistic people has been studied in adolescence and adulthood, with elevated rates of most conditions being reported. However, this has been little studied taking a dimensional approach to autistic traits and in older age. Methods A total of 20,220 adults aged 50–81 years from the PROTECT study reported whether they experienced persistent sociocommunicative traits characteristic of autism. Approximately 1%, 276 individuals, were identified as endorsing elevated autistic traits in childhood and currently, henceforth the “Autism Spectrum Trait” (AST) group. An age- and gender-matched comparison group was formed of 10,495 individuals who did not endorse any autistic behavioral traits, henceforth the “Control Older Adults” (COA) group. Differences between AST and COA groups were explored in self-reported psychiatric diagnoses, self-reported symptoms of current depression and anxiety, and self-reported physical health diagnoses. Associations were also examined between autistic traits and health across the whole sample. Results The AST group reported significantly elevated rates of psychiatric diagnoses compared to the COA group. Additionally, the AST group showed significantly higher self-reported symptoms of current depression and anxiety than the COA group. However, few differences were observed in individual physical health conditions, and no differences in total co-occurring physical diagnoses between groups. Similar associations between autistic traits and health were also found taking a dimensional approach across the whole sample. Discussion These findings suggest that older adults with elevated autistic traits may be at greater risk of poorer mental, but not physical, health in later life. Future studies should incorporate polygenic scores to elucidate the possible genetic links between the propensity to autism/high autistic traits and to psychiatric conditions, and to explore whether those with elevated autistic traits experience particular barriers to mental health care.