Entirely nanostructured nanofibrilar-polyaniline/multi-walled carbon nanotube (NF-PANI/MWNT) composites with nanotube loadings as high as 50 wt% were synthesized via a facile in-situ chemical polymerization process. These are composed of a nanofibrilar polyaniline (NF-PANI) matrix in which multi-walled carbon nanotubes (MWNTs) are homogeneously embedded and partially covered by polyaniline. Stable and homogeneous aqueous dispersions in concentrations up to 10 mg/ml in water easily were prepared. For the first time, dispersions and casted films of this novel type of NF-PANI/MWNTs composites are characterized. Both, dispersions and films reveal the typical behavior of PANI with slightly changed redox values and with fast reaction kinetics due to the presence of MWNTs. Conductivity of drop cast films reveal values of 20 to 50 S/m. Local SPM measurements confirm the intrinsic fibril structure. Individual fibrils show both semiconducting and metallic behavior with values up to 100 S/m. This new class of nanostructured NF-PANI/MWNT composites with its water-based processing possibilities as well as with its conducting and electrochromic effects will contribute to further progress in the field of smart plastic electronics.