During the COVID-19 pandemic, drastic measures to interrupt SARS-CoV-2 infection chains were implemented. In our study we investigated the consequences of pandemic related restrictions on the social, psychological, and physical well-being of institutionalized adults with intellectual and developmental disabilities. Methods: Online survey among professional caregivers in 71 residential groups, caring for 848 residents. Findings: (i.) A lack of participation concerning infection protection measures of the residents, their relatives, and their caregivers; (ii.) A 20% increase in doctor contacts during the pandemic; (iii.) A considerable deterioration in at least one item of the subdomains mood (49%), everyday skills (51%), social interaction (29%), exercise and coordination skills (12%), behavior (11%) and cognition and communication (7%); (iv.) A deterioration of the overall condition in 41%; Summary: Intensive attempts should be made to find individual and less categorical contra-infectious measures without questioning the basic everyday needs of people with intellectual and developmental disabilities.