This paper presents the first successful application of vinyl polymer/graphene-based nanocomposites in corrosion protection. Well-dispersed polystyrene (PS)/modified-GO nanocomposites were successfully prepared using in situ miniemulsion polymerisation. The as-prepared nanocomposites exhibit superior anti-corrosion properties compared with pure PS, in which the corrosion protection efficiency increased from 37.90% to 99.53% with the incorporation of 2 wt% modified GO in the PS polymer matrix. The thermal stability and mechanical properties also greatly improved compared with pure PS. The incorporation of 2 wt% modified GO in the PS polymer matrix increased the thermal decomposition temperature (T_d) from approximately 298 to 372 °C, and the storage modulus increased from 1808.76 to 2802.36 MPa. This paper attributes the substantially improved properties to the nearly complete exfoliation of the modified-GO dispersion, which greatly enhanced the modified-GO/PS interfacial bond strength and gas barrier properties.