In this study, we consecutively recruited treatment-seeking young autistic adults without intellectual impairment aged 16-30 years who presented to a mental health service and evaluated general health (distress, quality of life, and disability), functioning (work loss days and social functioning), and mood symptoms (depression, anxiety, and stress) in those diagnosed with autism spectrum disorder (n = 96). This group was compared to young adults presenting to the same service with primary mental health disorders (depression, n = 343; bipolar, n = 132; psychosis, n = 166; and anxiety, n = 303). This study also investigated the influence of mood symptoms on general health and functioning in the autism spectrum disorder group. Young autistic adults reported significant general health and functioning impairments that were of similar degree to those presenting with primary mental health disorders. Interestingly, the autistic group also reported similarly high levels of mood symptoms to those with primary depressive and anxiety disorders. In the autistic group, depressive symptoms were strongly associated with distress, quality of life, and work loss days, while stress symptoms were strongly associated with disability. This study highlights further research, and mental health services are required specifically targeting young autistic adults to address their significant unmet needs.