Background: People with intellectual disabilities (IDs) have a higher level of health needs, a higher level of which is unmet, compared with the general population. Health screening can detect unmet health needs, but it is unknown whether it effects beneficial health outcomes in the longer term. People with IDs are reliant on health management by proxy and there are many potential access barriers that may prevent health needs identified at screening from subsequently being met. This study aims to determine whether health gains can be detected 1 year after a health screening programme specific to the needs of adults with IDs. Methods: A total of 50 participants offered the health screen intervention were individually matched for gender, age and level of IDs with 50 control participants who received standard treatment only. Outcome measures after 1 year were semi-structured review of medical case notes, and semi-structured assessment with the people with IDs and their carer. Results: During the 1-year period, the incidence of health need detection was more than twice as great for intervention, compared with control participants (mean number of new needs was 4.80 compared with 2.26; P less than 0.001), and the level of met new health needs was greater (mean of 3.56 compared with 2.26; P = 0.001). The level of met health promotion needs was also greater (P less than 0.001), and more health monitoring needs were met for intervention compared with control participants (P = 0.039). Conclusions: This is the first study to demonstrate sustained benefits in health outcomes from a clinical intervention for adults with IDs compared with standard treatment alone. Its routine implementation is feasible, and would reduce health inequalities.