The purpose of this study is to explore the effect of Writing-to-Learn (WTL) strategy on undergraduates' conceptual understanding of electrostatics. The sample of the study was 54 university students registered at elementary school mathematics education department. While the experimental group was asked to conduct WTL activities like explanatory writing, the teachers in the control group carried on their classes with traditional methods like questioning. Conceptual discussions were made during the instruction in both groups. The data of the study were gathered by Electrostatics Conceptual Test. The data were analyzed both qualitatively and quantitatively. The results of the study showed that there was a significant difference between the levels of improvement of conceptual understanding in groups favoring the experimental group. It was suggested that writing-based activities should be used to improve the conceptual understanding of students in numerical calculation-based courses like physics and mathematics.