The barium titanate (BaTiO3) has properties that help to reduce or transform pollutant molecules such as sulfur dioxide (SO2). SO2 is one of the most pollutant gases present in the environment. For this reason, in this work, the adsorption of SO2 on the surfaces of the BaTiO3(001)-2×2, and Ag-doped BaTiO3(001)-2×2 has been investigated using first principles within the density functional theory (DFT). The SO2 molecule is adsorbed at different sites on the surface. Results show that the most stable configurations correspond to the BaTiO3(001)-2×2 surface at the B site, with an adsorption energy of −1.191 eV, and on the Ag-doped BaTiO3(001)-2×2 surface at the Ada-TiO site with an adsorption energy of −2.714 eV, both adsorption energies being in the chemisorption regime. The results revealed that the Ag-doped BaTiO3(001)-2×2 surface increases the adsorption energy for the SO2 molecule.