Until recently, autism in older adults went unrecognised. Although there has been more attention to autism in older adults in recent years, there is still a lot of unfamiliarity with the phenomenon and underdiagnosis in (mental) health care. Many care providers are reluctant to diagnose autism in later life, due to a lack of knowledge about autism in older adults and because there is still very little scientific knowledge available for this target group. Although several multidisciplinary guidelines for autism in adults prescribe that after the diagnosis psycho-education is the first step in treatment, psycho-education is still only offered in a few places in the Netherlands. Psycho-education is important to help older people gain knowledge about their autism, to help them understand and accept this diagnosis, in order to subsequently make the treatment of the problems, with which they turn to the mental health care, more appropriate and effective. The aim of this study is to contribute to better recognition and diagnosis of autism among older adults. This research also aims to improve a psycho-education program for older adults and investigate its effects. The scientific research question is whether training in ASD for health care professionals results in better recognition and detection of ASD in older adults, and whether participation in the psycho-education course for older adults, who have been diagnosed with autism, or have received a probability diagnosis ASD, contributes to improvement of mental health and quality of life.