Autism spectrum disorders (ASD) are difficult to detect in old age. This study examined if ASD symptoms in older adults (age > 60) can be detected with the Dutch informant personality questionnaire, (Hetero-Anamnestische Persoonlijkheidsvragenlijst, HAP) in a mental health setting. Patients with ASD (N = 40) were compared to patients with a different psychiatric diagnosis (N = 43; personality disorders excluded). The ASD group had significant higher scores on the scales ‘Socially avoidant behavior’, ‘Rigid behavior’ and ‘Unpredictable and impulsive behavior’. These scales were able to discriminate between individuals with or without ASD. The HAP can thus be used as a screening instrument for ASD symptoms in elderly patients. Further research is needed to clarify what items have the best predictive validity for ASD symptoms.