<p>Graphene oxide (GO), which can be synthesized inexpensively and in large quantities, is regarded as a promising starting material for electronic device applications due to its ability to recover electrical conductivity through reduction. However, oxygen-containing functional groups and structural defects introduced during the oxidation and reduction process significantly impair the electrical performance of reduced graphene oxide (rGO), posing a major challenge for practical implementation. In this study, we demonstrate that high-temperature thermal reduction in the presence of a carbonaceous gas not only facilitates the repair of vacancies in rGO thin films but also induces the homoepitaxial growth of two-dimensional graphene islands, guided by the underlying rGO template. By precisely controlling the growth driving force of the carbonaceous gas, epitaxial graphene islands were successfully formed, resulting in a significant improvement in electrical performance, with Hall mobilities reaching up to 365&#xa0;cm²/V·s. These results suggest that the homoepitaxial growth of graphene islands plays a crucial role in enhancing both the crystallinity and electrical properties of rGO thin films.</p>