ABSTRACT Purpose Despite the rising prevalence of developmental disabilities (DD) in the US, there remains insufficient training for healthcare professionals to care for this medically underserved population – particularly adults. The National Inclusive Curriculum for Health Education (NICHE) aims to improve attitudes and knowledge towards people with intellectual and developmental disabilities (PWIDD); herein we describe one such intervention. Method The intervention integrated didactic, panel presentation and clinical skills components into a 2nd year medical school curriculum. The didactic session, covering health and assessment of PWIDDs, history of IDD, stigma, etc., was co-taught by a developmental pediatrician, family medicine physician and social worker. A panel of 3 adult self-advocates (SAs) with DD and a parent of a child with DD spoke about their lived experiences. One week later, students practiced taking clinical histories of SAs within small group settings with adult PWIDDs, facilitated by medical school faculty. Students completed the NICHE Knowledge(49 items) and Attitudes (60 items) surveys. The evaluation analyzed pre/post intervention differences in a) knowledge and attitude scores overall and b) by student age, gender, intended medical specialty, and prior experiences with PWIDDs. Open-ended comments were analyzed with content analysis. Results Overall Knowledge scores increased from pre-to posttest (n = 85; 65[19] vs. 73[17], p = 0.00), while Attitudes score improved (i.e., decreased) (n = 88; 0.55 [.06] vs. 0.53 [0.06]); p = 0.00). Higher pretest knowledge was found among female identified students (vs. others; p = 0.01) and those knowing > = 5 PWIDD (vs < 5; p = 0.02). Students characterize their IDD training and experience prior to intervention as ‘lacking’ and described the sessions as effective. Conclusions A brief (4 hours total) intervention was associated with modest but significant improved knowledge and attitudes towards PWIDDs. Replication and sustainability of this and other NICHE interventions are needed to fill gaps in PWIDDs’ health care.