This study aimed to develop and evaluate the validity and reliability of dentists' radiation protection knowledge, attitudes, and practices (DRP-KAPs) questionnaire. This study was conducted using a stepwise approach. In the first step, items were generated to determine the relevant content and domains after a thorough literature review. In the second step, the content validity of the questionnaire was assessed by seven experts using face and content validity. The content validity index for relevance and clarity (I-CVI, S-CVI/Av, and S-CVI/UA) and the content validity ratio (CVR) were performed. Then, the questionnaire was pre-tested with 10 dentists for face validation. In the third step, reliability was assessed using internal consistency (Kuder-Richardson-20 (KR-20) and Cronbach's alpha) and test-retest (Kappa and intraclass correlation coefficient [ICC]) methods by filling out the questionnaire by 100 dentists practicing in the Rabat-Salé-Kénitra region, in Morocco. The finalized DRP-KAPs questionnaire contains 41 items covering knowledge, attitudes and practices (KAPs). The I-CVIs, S-CVI/UA and S-CVI/AV and CVR values of the 41 items were ≥0.86 for each item, ≥0.82, ≥0.97, and ≥0.71, respectively. With regard to internal consistency reliability, the KR-20 coefficients for the knowledge and practice domains were 0.70 and 0.68, respectively, and the Cronbach alpha for the attitude domain was 0.73. The DRP-KAPs questionnaire has good reliability with the ICC coefficients for attitude items ranging from 0.57 to 0.95 and Kappa coefficients for knowledge and practice items ranging from 0.64 to 1 and 0.77 to 1, respectively. The developed DRP-KAPs questionnaire was found to be a noteworthy tool for assessing radiation protection among dentists, with acceptable internal consistency, good ICC and Kappa coefficients, and good content validity indices.