In this study, it was aimed to develop a rubric for evaluating the critical writing skills of primary school fourth-grade students. The research was designed in quantitative research method and scanning design. The study group of the research consists of 215 students studying in the fourth grade of five different primary schools determined by the purposeful sampling method, taking into account their gender and socioeconomic status. Research data were collected during the development stages of the rubric and lasted for four weeks. In this process, opinions were received from 54 classroom teachers, 12 Turkish teachers, 8 doctoral students continuing their graduate education in the field of Classroom Education and Turkish Education, and 16 academicians who are experts in the field of Basic Education. In addition, the students in the study group were asked to write critical articles and the written products were evaluated through the developed scoring key. The collected data were analyzed with a statistical program. In order to ensure internal consistency in the research, Cohen's Kappa coefficient was determined in order to determine the reliability of the evaluations of the raters who scored the data. Cronbach Alpha coefficient was determined in order to determine that the dimensions and items in the developed rubric were items that were consistent with each other and that examined the same feature. As a result of the findings, it was concluded that there was a high level of consistency between the evaluations made by different raters. In addition, in line with the expert opinions received during the development of the rubric, It was concluded that the rubric exactly measured what was intended to be measured and the rubric was valid and reliable.