We propose and characterize a novel 2D material with a perovskite structure, Sr2TaO4 monolayer. Using a first principles approach, we study the stability, elastic and electronic properties of the 2D-Sr2TaO4 system. In this metallic monolayer system, the tantalum atom is surrounded by six oxygen atoms in an octahedral configuration. The rotation of the octahedra structures yields antiferrodistortive distortions favoring a phase transition. We have demonstrated the stability of this perovskite-like monolayer using phonons, molecular dynamics, and elasticity criteria.