In this study; The effect of the Self-Regulated Strategy Development Model (SRSD) on the development of critical writing skills of primary school fourth grade students was examined. The research was designed in a mixed model and patterned in the type of action research. In addition, "Single Group Pretest-Posttest Weak Experimental Design", which is one of the experimental design types, was used in the research. Research data; critical writing scale, activity papers, focus group interviews, researcher's diary and observation forms. The study group of the research consisted of 21 students studying in the fourth grade of a primary school in Aydın in the 2021-2022 academic year. Quantitative data obtained from the research were analyzed using the "Dependent Sample t-test" and "Pearson Product Moments Correlation". The qualitative data of the research were obtained through observation and focus group interviews and interpreted with thematic coding technique. At the end of the research, there was a statistically significant difference between the scores of the students in the pretest and posttest; It was observed that there was a statistically significant, positive and high level correlation between the scores they got from the posttest and retention tests. In line with the observations and interviews made in the research, it can be said that the critical writing education carried out with the activities designed with the ÖDSG Model contributes to the development of the critical writing skills of the fourth grade primary school students.