Background: During the past years the provision of mental healthcare for adults with intellectual disabilities (ID) has repeatedly been criticized; however, the number of relevant studies is still relatively few. Objective: The aim of the present study was to identify determinants for utilization of mental healthcare services and prescription of psychotropic medication in adults with mild to moderate ID. Material and methods: Analyses were based on data from 417 adults with mild to moderate ID, which had been collected within the cross-sectional MEMENTA study in three different regions of Germany. Logistic regression analyses were conducted to identify clinical and sociodemographic variables as predictors of utilization of mental healthcare services (n = 282) and psychotropic medication (n = 351). Results: Utilization of healthcare services and psychotropic medication were both associated with mental disorders and problem behavior. In addition, the likelihood of being treated with psychotropic medication and antipsychotic drugs was higher in adults living in residential homes. Conclusion: The findings indicate a lack of adherence to existing guidelines in the treatment of adults with ID living in residential homes.