The study examined the effect of wordless picture book use on the story writing skills of third-grade primary school students. The quantitative part of the study, which utilized an explanatory mixed-methods design, employed a quasi-experimental design, while the qualitative part used a case study design. The study included thirty-one students selected through convenience sampling from Atatürk Primary School in Altınyayla district of Sivas. In the study, third-grade primary school students were asked to write stories on the topic of “values” as a pre-test and post-test, and the stories written by the students were evaluated according to the “Written Expression Assessment Form.” In addition, semi-structured interviews were conducted with 9 randomly selected students from the experimental group about the wordless picture book story writing activity; the data obtained from these interviews were examined using descriptive analysis methods. The analysis revealed that although writing activities using wordless picture books and story writing activities alone did not make a significant difference to the story writing skills of third-grade primary school students, both activities were found to improve students’ story writing skills.