Nanofiber-like mesoporous γ-Al2O3 was synthesized using freshly prepared boehmite sol in the presence of triblock copolymer, P123 following evaporation-induced self-assembly (EISA) process followed by calcinations at 400°C–1000°C. The samples were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), N2 adsorption–desorption, and transmission electron microscopy (TEM). The adsorption efficiency of the samples with Congo red (CR) was studied by UV–vis spectroscopy. XRD results showed boehmite phase in the as-prepared sample while γ-Al2O3 phase obtained at 400°C was stable up to 900°C, a little transformation of θ-Al2O3 resulted at 1000°C. The Brunauer-Emmett-Teller surface area of the 400°C-treated sample was found to be 175.5 m2g−1. The TEM micrograph showed nanofiber-like morphology of γ-Al2O3. The 400°C-treated sample showed about 100% CR adsorption within 60 min.