Abstract: The electrochemical properties of graphene-polyaniline (PANI) hybrids are largely determined by their microstructures and the distribution of PANI on the graphene network. Uniform hybridization of each component is critical to avoid the re-stacking of the graphene sheets and the agglomeration of PANI nanoassemblies during the use of the hybrids. Conventional strategies, such as layer-by-layer assembly or electrochemical in-situ polymerization, involve intricate procedures, making it difficult to achieve the large-scale production of the hybrids. We report a completely miscible cosolvent consisting of N, N-dimethylformamide and water that solves this problem and was used to produce graphene-PANI hybrid flexible fibers. It was found that the composite fiber had a homogeneous microstructure with PANI nanoassemblies uniformly distributed on the graphene sheets, and had outstanding electrochemical properties, much better than the counterpart fabricated using only water as the solvent. The work proposes a universal but simple strategy to achieve the mass production of graphene-PANI hybrids or similar materials with uniform hybridization of the two components.