This study aims to investigate the effect of 5E Learning Model-based Essay Writing course design and implementation on the achievement level of 12th grade high school students in Essay Writing Course. The teaching and development of writing skills in foreign language education is very important, but it is a known fact that our foreign language education presents problems even in the level of middle and higher education in the foreign language education system. In this respect, the development of writing skills and the improvement of the lessons are very important. The study is a case study with mixed method in which both qualitative and quantitative data collection procedures and instruments such as achievement tests, peer feedback form, students’ progress check form, and teacher performance observation form are employed together. In the present study, qualitative data, collected by means of peer evaluation, student progress check and teacher performance observation, is subjected to descriptive analysis whereas quantitative data, collected by means of Essay Writing achievement tests which are applied to twenty-two 12th grade students before and after the instruction and implementation of 5E Learning Model-based Essay Writing Course as pre- and post-test, is analyzed by paired sample t-test. According to the results of the analysis, it can be said that the implementation of 5E Learning Model-based Essay Writing course has a positive effect on the achievement level of students in Essay Writing Course.