Polyaniline (PANI) grafted Graphene Oxide (GO), GO–PANI nanocomposite exhibits interesting pH dependent tunable photoluminescence. Exciting at 230 nm, a single emission band at 345 nm is observed and this band is shifted from UV to blue region by decreasing the pH less than 3. Aqueous dispersion of GO–PANI (pH=4.6) shows dual fluorescence at 345 nm and 405 nm upon excitation at 280 nm indicating the presence of two emissive moieties. At pH<3, single fluorescence peak at 410 nm is observed by exciting GO–PANI at 280 nm, whereas the emission band is centered at 345 nm when pH is more than 5. Instead of the peaks at 230 nm and 280 nm in alkaline region, a peak at 250 nm has been obtained in the excitation spectra (at pH<3) monitored at 410 nm. This observation suggests the formation of a new ground state species. The presence of this species is further supported by a fluorescence lifetime components at 410 nm. From the luminescence behavior of GO–PANI and electronic characteristics of GO and PANI at low pH, one may consider the formation of the species as a result of charge transfer interaction between GO and PANI. © 2016 Elsevier B.V.