Scalable water-dispersible graphene (eGPNc) powders were prepared with consecutive chlorosulfonic acid (CSA)/H2O2 and methylmorpholine N-oxide monohydrate (NMMOm) treatments, followed by the common filtering, sonication, and drying processes. The yield of graphene from expanded graphite (EG) powders prepared by the combined CSA/H2O2 and NMMOm treatments (3.0 wt%) was more than five times that from only the NMMOm treatment (0.6 wt%). The produced eGPNc powders had an almost defect-free graphitic structure with good redispersibility in water and an electrical conductivity of 86.9 S/cm from the filtered eGPNc film. The eGPNc film was dispersed at 0.28 mg/mL in water after centrifugation of the 2 mg/mL aqueous solution at 5000 rpm. The aqueous eGPNc solution was utilized as the reaction medium for the in situ polymerization of pyrrole to produce the polypyrrole (PPy)/graphene nanocomposite. The capacitance of PPy measured from cyclic voltammetry (CV) was improved from 122.8 to 278.6 F/g by loading 1 wt% eGPNc onto the nanocomposite. The capacitance of PPy after 1000 CV cycles was improved from 54.0% to 91.0% by loading 3 wt% eGPNc onto the nanocomposite. This improvement in the capacitance and capacitance-stability is due to the in situ formation of PPy in the well-dispersed aqueous graphene solution. Thus, this simple in situ preparation of PPy with eGPNc in water demonstrated the potential for the diverse applications of water-dispersible eGPNc in various water-based systems such as conducting inks, silver wires, and watersoluble conducting polymers (e.g. poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PSS/PEDOT)) for improving their electron conductivity and stability.