A one-pot, soft-chemistry, surfactant-assisted co-assembly approach to prepare La(1-x)Sr(x)WnO(3) (LSM)/Y2O3-stabilized ZrO2 (YSZ) nanocomposites for use as solid oxide fuel cell (SOFC) cathodes has been investigated. This material with sub-hundred nanometer grain sizes for each phase is the first such nanocomposite where aqueous-based precursors of each component are incorporated in a single synthetic step. This approach utilizes the co-assembly of an anionic yttrium/zirconium acetatoglycolate gel, cetyltrimethylammonium bromide as the cationic surfactant template, and inorganic La, Mn, and Sr salts under alkaline aqueous conditions. The resulting as-synthesized product is an amorphous mesostructured organic/inorganic composite, which is transformed to a mesoporous inorganic oxide with nanocrystalline YSZ walls upon calcination. Calcination to temperatures above 600 degreesC lead to collapse of the mesopores followed by further crystallization of the nanocrystalline YSZ phase and a final crystallization of the LSM perovskite phase above 1000 degreesC. Both the fully crystalline LSMNSZ and,the mesoporous intermediate phase have been investigated for phase homogeneity by TEM energy-dispersive X-ray spectroscopy (EDX) mapping and spot analysis which confirm the dispersion of LSM within a YSZ matrix at the nanometer scale. Impedance spectroscopy analysis of LSMNSZ nanocomposite electrodes demonstrate a low polarization resistance of around 0.2 Omega cm(2) with an activation energy (E-a) as low as 1.42 eV. Cathodic polarization studies show stable current densities over a 40 h test demonstration.