Health disparities are documented between adults with intellectual and developmental disabilities (IDD) and neurotypical peers. As progress has been slow in improving health outcomes in people with IDD, the aim of this retrospective study was to compare effectiveness of a new Cross-Systems Care Integration (CSCI) model of care coordination to standard care coordination for 927 adults with IDD receiving Medicaid services in central Colorado from 2014 through 2017. Health care cost risk weight decreased (not statistically significant) only in individuals receiving the CSCI intervention. Depression diagnoses remained statistically unchanged, while both hypertension and hyperlipidemia significantly improved in patients receiving CSCI. Further study is warranted to extend duration of study and to examine additional study variables such as health-related quality of life.