Background/Purpose: The study aimed to develop a rubric to measure students' critical-thinking skills within a multicultural education scope. Materials/Methods: The study's participants were faculty members, teachers, and students, determined according to convenience sampling based on predetermined criterion. Initially, a story-based test and critical-thinking rubric were prepared and then validity studies conducted on these products. Subsequently, the prepared test and rubric were applied to fourth-grade elementary school students, with the data scored by their teachers, and reliability studies were then conducted. During the study's analysis, scope, validity index and ratio, agreement percentage, correlation coefficient, Kendall's concordance coefficient, and Cronbach's alpha coefficient were all examined. Results: The collected data were evaluated according to statistical analysis and the obtained findings showed the developed rubric to be both valid and reliable. The results revealed that the rubric developed to evaluate critical-thinking skills in a multicultural education scope was deemed to be an effective tool to assist teachers in measuring and evaluating students' critical-thinking skills. In addition, use of the rubric can contribute to identifying and implementing strategies to improve students' critical-thinking skills. Conclusion: The study developed effective tools for practitioners and decision-makers in the field of education to measure and develop students' critical-thinking skills. In particular, use of the developed rubric in the evaluation of students' critical-thinking skills presents a significant step in increasing success in education and supporting students' future academic and professional achievements. In conclusion, this research demonstrated the validity and reliability of a rubric that may be used as an effective tool for the evaluation and development of critical-thinking skills in education.