[en] Highlights: • The well-dispersed PGO have strong interfacial interactions with PVA. • PVA/PGO nanocomposites are prepared by a convenient and environmentally friendly method in aqueous solution. • PVA/PGO nanocomposites show an integrated performance of high thermal resistance, good water barrier properties and electrical properties. - Abstract: In this paper, poly(vinyl alcohol) (PVA)/poly(dopamine)-functionalized graphene oxide (PGO) nanocomposites with high performance were prepared by an environment-friendly and facile strategy. GO was firstly functionalized and simultaneously reduced by poly(dopamine) to yield PGO. Then it was mixed with PVA in aqueous solution to make PVA/PGO nanocomposites. Transmission electron microscopy revealed that the PGO nanosheets are well dispersed and randomly oriented throughout the PVA matrix. At the same time, the thermal properties and water barrier properties of the PVA/PGO nanocomposites have been strikingly enhanced by the incorporation of PGO. The degradation temperature of the nanocomposites is more than 30 °C higher than that of pure PVA by the addition of 0.7 wt% PGO, which shows good thermal stability. The water vapor permeability of the nanocomposites also decreases to 0.71 × 10⁻¹² g cm/(cm² s Pa), corresponding to 80% reduction than that of pure PVA. Moreover, the PVA/PGO nanocomposites also present enhanced conductive properties. The PVA/PGO nanocomposites with such outstanding properties show great promising applications in the fields of packaging, electronics, fuel cell industry, fiber, and so on.