Herein, we report the facile synthesis, detailed characterizations and environmental remediation applications of surfactant functionalized tungsten oxide (WO3) nanoparticles (NPs). Different cationic surfactants with different chain lengths and counter ions such as cetylpyridinium chloride (CPyC), cetylpyridinium bromide (CPyB), hexadecyltrimethyl ammonium bromide (HTAC) and tetrade-cyltrimethyl ammonium bromide (TTAB) were used. These templates served a dual purpose: firstly, functionalization of the nanoparticles and secondly, control the stoichiometry, thus preventing the agglomeration in the nanoparticles. The as-synthesized nanoparticles were characterized in detail to check the morphological, structural, compositional, optical and photocatalytic properties. The detailed characterizations revealed the mono-dispersity of spherical shaped nanoparticles that are grown in high density, possessing monoclinic phase. Further, the functionalized WO3 nanoparticles were used as efficient photocatalysts for the photocatalytic degradation of highly toxic but immensely used azo dye, i.e. congo-red (CR). The photocatalytic degradation reaction conditions were optimized by carrying out various concentration dependent experiments (both photocatalyst and initial dye concentration) and also optimizing irradiation time. The detailed photocatalytic experiments revealed that the photo degradation followed second order kinetics and the degradation efficiency was over 95% for all the surfactant functionalized WO3 nanoparticles. Importantly, this paper presents the comparison of the photo degradation activities of prepared functionalized WO3 nanoparticles towards the differences in the chain length, counter-ions and arrangement or orientation of surfactants on the nanoparticle surfaces. (C) 2015 Elsevier B.V. All rights reserved.