Abstract Research involvement among registered dietitians (RDs) is important in advancing dietetics practice and ensuring high-quality and cost-effective health care. There are no standardized approaches to measuring levels of research involvement. The aim of the study was to develop a standardized measure of research involvement and test its validity and reliability among RDs. The Research Involvement Questionnaire (RIQ) was developed and underwent content validation, resulting in a content validity index of 0.92. A postal questionnaire survey of RDs was undertaken at two time points. RDs were purposively selected and, based on their number of publications and grants, were assigned by the authors to one of four levels of research involvement: evidence-based practice, collaborating on research, leading research, and leadership in research. Of 192 questionnaires mailed, 111 RDs (58%) returned the first RIQ, of whom 82 (74%) also returned the second RIQ. Total scores and scores for each level were higher for RDs with higher levels of research involvement (P<0.001). RDs assigned by the RIQ to higher levels of research involvement had higher qualifications; were qualified for longer; and had greater evidence of research output, including journal publications and grants (P<0.001). There was excellent internal consistency as measured using Cronbach's coefficient (α=.98). The level of research involvement assigned by the RIQ and by the purposive selection process agreed on 76% of occasions, indicating substantial agreement beyond chance (κ=0.67; P<0.001). The level of research involvement assigned by the RIQ at two time points agreed on 86% of occasions, indicating almost perfect agreement beyond chance (κ=0.81; P<0.001). A valid and reliable questionnaire has been developed to measure research involvement among RDs, providing a useful tool for evaluating and supporting members of the profession to become more involved in research.