This study investigates the role of clause complexity in students' academic writing, focusing on the application of Systemic Functional Grammar (SFG) symbols to create persuasive and coherent discourse. Employing a qualitative single-case method, the analysis examines a specific text on the dangers of smoking produced by students. The findings showcase the students' effective use of varied clause types and relationships, as well as their ability to present a systematic and logical flow of ideas supported by factual evidence. The results emphasize the importance of mastering multiple elements, such as utilizing diverse clause types and maintaining a strategic narrative flow, for successful academic writing. These insights can serve as valuable information for educators and academic writers alike, offering a deeper understanding of the implications of clause complexity and its role in fostering effective communication in academic writing.