Background: It is hypothesized that knowledge towards ionizing radiation (IR) protection measures is lacking among newly graduated dentists from Egypt and Saudi Arabia. The purpose of the present questionnaire-based study was to compare the IR protection knowledge among newly graduated dentists from Egypt and the Kingdom of Saudi Arabia (KSA). Methods: The present investigation was a questionnaire-based study and had a cross-sectional observational analytical design. Newly graduated dentists were defined as individuals who had graduated from a credentialed dental institution within the past 36-months. The questionnaire was related to knowledge about radiation safety, awareness and practices. The questionnaire comprised of 17 multiple choice questions. Questionnaires in which all the 17 questions were not answered or had missing pages were excluded. Odds ratios were computed for the number of correct and incorrect responses and 95% confidence intervals were determined. Individuals that provided up to 40%, 41% to 70% and >70% correct answers were categorized as having “low competence”; “moderate competence” and “high competence” in IR knowledge. p-values less than 0.05 were considered statistically significant. Results: The mean percentage of correct answers provided by dentists from Egypt and KSA were 56.9% and 67.4%, respectively. There was no statistically significant difference in the percentages of correct responses for the 17 questions submitted by respondents from Egypt and KSA. The overall percentage of correct responses ranged between 40.2−71.2% and 45.4−81.4% for respondents from Egypt and KSA, respectively. The odds ratios and 95% confidence intervals showed no statistically significant correlation in the responses from respondents from Egypt and KSA for each of the 17 questions addressed. Conclusion: Newly graduated dentists from Egypt and KSA are moderately competent regarding IR doses and related safety measures. It is recommended that modifications in the undergraduate dental education curriculum with emphasis on IR safety and practice would help enhance the knowledge and competence of students and newly graduated dentists. Moreover, routine continuing dental education seminars/programs may help enhance the IR knowledge of dental students and dentists.