BACKGROUND: The relationship between handwriting and executive function has been explored in numerous studies. However, limited research has focused on the relationship between handwriting and prefrontal cortex (PFC) activity, which underpins executive function and writing processes. Additionally, differences in frontal lobe activity during writing between adults and children remain inadequately understood. This study aimed to investigate developmental changes in the prefrontal cortex and their neural basis during writing activities in children and adults. METHODS: In this study, a pen tablet and functional near-infrared spectroscopy (fNIRS) were used to compare adult and pediatric writing dynamics and PFC function during two writing activities. The stimuli consisted of two line-drawing tasks designed to minimize linguistic influence, with two conditions (trace and predict) applied to each task. PFC activation was examined across the right, middle, and left regions. Oxygenated brain activity was quantified by converting oxygenated hemoglobin values obtained from fNIRS to z-scores. RESULTS: The line length, an index of writing dynamics, was consistently shorter in children compared to adults across all tasks and conditions. Regarding brain function, the right PFC exhibited greater activation in adults during the predictive periodic line pattern drawing condition. CONCLUSION: These findings suggest that the lateralization of the right PFC plays a critical role in the development of executive function, which is integral to writing development.