Abstract: Bamboo-plastic composites (BPC) hold significant promise for advancing sustainable development strategies. However, their limited mechanical performance has hindered widespread adoption in load-bearing engineering structural applications. In this study, continuous basalt fibers (CBF) were surface-modified via a melt-impregnation process using ethylene–vinyl acetate (EVA) copolymer, and subsequently incorporated into a BPC matrix to fabricate EVA-modified, continuous basalt fiber-reinforced bamboo-plastic composites (EBPC) with markedly enhanced mechanical properties. Results demonstrate that EVA modification substantially improves interfacial adhesion between the CBF and the BPC matrix, leading to a 199.78% increase in interfacial shear strength. Correspondingly, the tensile, impact, and flexural strengths of the EBPC was enhanced by 22.07%, 19.98%, and 9.29%, respectively, relative to unmodified composites. Dynamic mechanical analysis further confirms improved interfacial compatibility. Moreover, EVA incorporation significantly enhances the composite’s water resistance: both water absorption and thickness swelling were suppressed, and after 7 days of water immersion, the retention rates of flexural, impact, and tensile strengths remain above 80%.