The aim of this study is to investigate the effects of using multiple writing-to-learn activities on the critical thinking skills and dispositions of prospective teachers. For this purpose, the current study employed an embedded mixed-methods design and was carried out with 34 prospective Social Studies teachers who are studying at a public university. Research data were collected with the California Critical Thinking Disposition Inventory, as well as using the Holistic Critical Thinking Scoring Rubric, and also, semi-structured interview forms. In the research process, a variety of writing activities such as letters, diaries, columns and news articles were used for learning purposes. The quantitative data obtained in the research were analyzed descriptively and predictively, while the qualitative data were subjected to content analysis. The results of the study revealed that the writing-to learn activities led the prospective Social Studies teachers to do research, use evidence, get to know different ideas, and evaluate what they learned in a holistic way. Such a situation made a significant difference on the critical thinking skills and critical thinking dispositions of the prospective Social Studies teachers. Given such a result, it is recommended to draw upon writing-to-learn activities in order to develop different courses, subjects and higher-order thinking skills.