ObjectivesThe prevalence of root caries is increasing globally, especially in the elderly population, and even though the number of patients with root caries lesions is augmenting, there are still many discrepancies in how dentists manage this condition. The present study aimed to develop and validate a questionnaire to evaluate how dentists diagnose, record and manage root caries lesions, and to verify the validity and reliability of this questionnaire.Materials and methodsAn expert panel developed a self-administered questionnaire survey with three domains: (1) dentists’ knowledge on diagnosis, recording, and managing root caries; (2) information about their current general clinical routines; (3) their demographics. The original English [E] version was translated into three different languages (French [F], German [G], Italian [I]), and subsequently back-translated into English by independent dentists. For the validation, 82 dentists (20–22 for each of the translated versions) accepted to answer the questionnaire at two different time-points (with 1-week interval). The data was quality checked. Construct validity, internal reliability, and intra-class correlation (ICC) were assessed.ResultsSeventy-seven dentists completed the questionnaire twice [E: 17;F: 19;G: 19;I: 22]. The mean ICC (standard deviation) was 0.98(0.03) forE, 0.90(0.12) forF, 0.98 (0.04) forG, and 0.98 (0.01) forI. Overall, the test–retest reliability was excellent (mean ICC (SD): 0.96 (0.08)). Furthermore, the questionnaire demonstrated good internal reliability (inter-observer reliability; Fleiss kappa: overall:0.27(fair);E:0.30 (fair);F: 0.33(fair);G: 0.33(fair);I: 0.89 (almost perfect)).ConclusionThe questionnaire was validated and is suitable to be used in the four languages to assess the knowledge of dentists on diagnosing, recording and managing root caries.Clinical significanceThe present questionnaire was validated and seems to be a good tool to evaluate how dentists diagnose, record, and manage root caries lesions both in its original (English) and its translated (French, German, and Italian) versions.Supplementary informationThe online version contains supplementary material available at 10.1007/s00784-022-04842-x.