Poly(3-hexylthiophene) (P3HT) supramolecular structures are fabricated on P3HT-dispersed reduced graphene oxide (RGO) monolayers and surfactant-free RGO monolayers. P3HT is able to disperse RGO in hot anisole/NN-dimethylformamide solvents, and forms nanowires on RGO surfaces through a RGO induced crystallization process. The TEM and AFM investigation of the resultant P3HT/RGO composites shows that P3HT nanowires grow from RGO, and connect individual RGO monolayers. Raman spectroscopy confirms the interaction between P3HT and RGO, which allows the manipulation of the RGO electrical properties. Such a bottom-up approach provides interesting graphene-based composites for nanometer-scale electronics.