We report the facile preparation of the conductive polymer composites containing the mixed-valence tetrathiafulvalene (TTF) nanofibers and their applications as all-organic transparent conductive materials. TTF can be used as a nanofiller for transforming conventional polymers to conductive materials. Self-assemble nanofibers of the neutral and radical cation of TTF can be formed in the polymer solutions during the film deposition, and the resulting composite films with several micron thickness can serve as the conductive material with high transparency. Several kinds of conventional polymers, such as polystyrene, poly(methyl methacrylate) (PMMA), and poly(vinylpyrrolidone), can be used as a polymer matrix of the composites. The conductivities of the PMMA film containing 35 mol % of the mixed-valence TTF and the PEDOT-PSS film showed similar values (2.8 x 10(-2) and 5.4 x 10(-1) S/cm, respectively). In contrast, the normalized transmittance of the PMMA film by 1-mu m thickness greatly increased (96%/mu m) when compared with that of the PEDOT-PSS film (10%/mu m). In addition, the degradation of the conductivity of the nanofibers by heating and aging was effectively suppressed in the composite samples. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6441-6450, 2009