Background: This study examines recent trends in the age-at-death disparity between adults with and without intellectual and/or developmental disabilities in the United States. Method: Data were from the 2005-2017 U.S. death certificates. Average age at death was compared between adults whose death certificate did or did not report an intellectual and/or developmental disability. Results: Age at death increased minimally for adults without, but markedly for adults with intellectual and/or developmental disabilities. As a result, the age-at-death disparity decreased: 2.2 years between adults with/without intellectual disability; 1.9 years between adults with/without Down syndrome; 2.7 years between adults with/without cerebral palsy; and 5.1 years between adults with/without rare developmental disabilities. Conclusion: Evidence from this study demonstrates that the age-at-death disparity between adults who did or did not have an intellectual and/or developmental disability reported on their death certificate continues to decrease, but the magnitude of the remaining disparity varied considerably by type of disability.