The study aims to examine the effect of the Four Square Writing Method (FSWM) on the writing anxiety of the learners of Turkish as a foreign language at the B2 level. The mixed-methods sequential explanatory design was applied, and 50 students at the B2 proficiency level who studied at the Turkish Teaching Practice and Research Center (BAIBU TÖMER) at Bolu Abant Izzet Baysal University in the 2020-2021 academic year were selected through the purposeful sampling. The quantitative data were obtained with a weak experimental design consisting of a pre-test and a post-test, while the qualitative data consisted of interviews with the participants. As data collection instruments, the Writing Anxiety Scale (WAS) developed by Sen and Boylu (2017) and the Semi-Structured Interview Form designed by the researchers were used. Quantitative data were analyzed by hypothesis testing, whereas qualitative data were scrutinized using content analysis. The quantitative data showed that the FSWM had a statistically significant effect on the writing anxiety of the learners of Turkish as a foreign language. On the other hand, the qualitative findings were categorized into two main themes: "writing skills" and "affectivity." The writing skills category included 13 codes and 72 views; "general, transition, and linking expressions, developing strategies, developing thinking skills, learning vocabulary, enhancing writing style, planning in writing, graphic organizer, drafting, collaborative writing, organization, writing quality, and generating ideas. The affectivity category consisted of 5 codes and 31 views, including relaxation, enjoyment, motivation, increased self-confidence, and dislike. The findings determined that the FSWM played a role in positively affecting writing anxiety, contributing to the development of writing skills, promoting participants' psychological comfort, allowing them to have a fun time, gaining self-confidence, and motivating them to write. Lastly, the study detailed the aspects where the qualitative findings supported the quantitative results contributing to the interpretation of the data.