Natural bamboo-based fiber composites offer unique advantages in terms of renewability and eco-friendliness. However, challenges such as dimensional stability in outdoor applications must be addressed. This study reports a straightforward method to impregnate oriented bamboo fiber mats with natural persimmon lacquer and ferrous sulfate to fabricate bamboo scrimber composite. The tannic acid from the persimmon lacquer formed complexes with iron ions, enhancing the water resistance of the bamboo scrimber composite, though slightly negatively impacting its mechanical properties. These complexes promoted a denser carbon structure, and the resulting metal oxides act as smoke inhibitors, reducing the total smoke production rate by 62.43%. Furthermore, the bamboo scrimber composite exhibited excellent mildew resistance, hydrophobicity, and color stability, making it suitable for outdoor flooring and furniture applications. The findings provide a green processing strategy to prepare high-performance bamboo-based fiber composites for outdoor construction and furniture use.