Background: Direct support professionals' (DSPs') attitudes toward nutrition are important for supporting a healthy lifestyle of persons with intellectual disabilities. However, there are no instruments to measure it. The aim of this study was to compose a questionnaire and determine its internal validity. Method: The previously validated Health Enhancing Physical Activity questionnaire was adapted into the Attitude of DSPs for Health Enhancing Nutrition (ADSP-HENU) and completed by 31 DSPs. The internal validity of the questionnaire was investigated by Cronbach's Alpha and an exploratory non-parametric item response analysis (NIRT). Results: The internal consistency by Cronbach's Alpha was good (0.87, 95% CI [0.81-0.94]). NIRT showed monotonicity with wide confidence bounds and sufficient point polyserial correlations of the items. This indicates that each attributes to the overall measured attitude. Conclusion: The internal validity of the ADSP-HENU is promising, and it can be used in daily practice for evaluation or adapting interventions to DSPs' needs.