In this study, we predicted new two-dimensional tetragonal structures of t-Mn2X2 (X = S, Sb) sheets on the basis of first-principles plane wave calculations within density functional theory with Hubbard U model. Stability tests such as phonon spectrum calculation and molecular dynamic simulations reveal that the 2D t-Mn2X2 structures are dynamically and thermally stable at least in room temperature. Our theoretical calculations have shown that t-Mn2X2 structures have two Raman active and seven infrared active modes. The t-Mn2Sb2 sheet exhibits metallic property, whereas t-Mn2S2 shows semiconducting property with a 0.68 eV indirect bandgap. Exploring of the favorable magnetic orientation calculations revealed that both 2D t-Mn2X2 structures prefer antiferromagnetic spin configuration. Estimated critical temperatures for the phase transition from antiferromagnetic spin order to paramagnetic case are 720 K and 545 K for t-Mn2S2 and t-Mn2Sb2, respectively. These relatively high Neel temperatures and their suitable electronic properties for many applications clearly qualify that the 2D t-Mn2X2 sheets can be a good candidate for room temperature antiferromagnetic device applications. Published under license by AIP Publishing.