Amine-functionalized silica sorbents have been widely investigated for post-combustion CO2 capture at low temperature. In previous studies, amine-functionalized silica sorbents were prepared using a synthetic hierarchically porous silica, which is not commercially available in large quantities, because porous silica support structures strongly influence CO2 capture performance. Here, we propose a feasible and facile fabrication method for amine-functionalized silica sorbents using 3-aminopropyltrimethoxy silane (APTS) and fumed silica (FS), where APTS serves as both an active material and a binder. The APTS-functionalized FS sorbents have large amounts of active amino groups and porous structures and demonstrate good multicycle stability with excellent CO2 capture performance. In addition, cetyltrimethylammonium bromide was found to improve the diffusion pathway of CO2, leading to enhanced CO2 capture capacity because of the suppression of excessive condensation during preparation. Therefore, the APTS-functionalized FS sorbents could be cost- and energy-efficiently prepared using a novel one-pot synthesis method; the resulting sorbents exhibit excellent CO2 capture performance.